What is the definition of the word tornado

Tornado
A tornado approaching Elie, Manitoba, Canada.
Season	Primarily spring and summer, but can occur at any time of year with the right atmospheric conditions
Effect	Wind damage

A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone,^[1] although the word cyclone is used in meteorology to name a weather system with a low-pressure area in the center around which, from an observer looking down toward the surface of the Earth, winds blow counterclockwise in the Northern Hemisphere and clockwise in the Southern.^[2] Tornadoes come in many shapes and sizes, and they are often visible in the form of a condensation funnel originating from the base of a cumulonimbus cloud, with a cloud of rotating debris and dust beneath it. Most tornadoes have wind speeds less than 180 kilometers per hour (110 miles per hour), are about 80 meters (250 feet) across, and travel several kilometers (a few miles) before dissipating. The most extreme tornadoes can attain wind speeds of more than 480 kilometers per hour (300 mph), are more than 3 kilometers (2 mi) in diameter, and stay on the ground for more than 100 km (60 mi).^[3][4][5]

Various types of tornadoes include the multiple vortex tornado, landspout, and waterspout. Waterspouts are characterized by a spiraling funnel-shaped wind current, connecting to a large cumulus or cumulonimbus cloud. They are generally classified as non-supercellular tornadoes that develop over bodies of water, but there is disagreement over whether to classify them as true tornadoes. These spiraling columns of air frequently develop in tropical areas close to the equator and are less common at high latitudes.^[6] Other tornado-like phenomena that exist in nature include the gustnado, dust devil, fire whirl, and steam devil.

Tornadoes occur most frequently in North America (particularly in central and southeastern regions of the United States colloquially known as Tornado Alley; the United States and Canada have by far the most tornadoes of any countries in the world).^[7] Tornadoes also occur in South Africa, much of Europe (except Spain, most of the Alps, Balkans, and northern Scandinavia), western and eastern Australia, New Zealand, Bangladesh and adjacent eastern India, Japan, the Philippines, and southeastern South America (Uruguay and Argentina).^[8][9] Tornadoes can be detected before or as they occur through the use of pulse-Doppler radar by recognizing patterns in velocity and reflectivity data, such as hook echoes or debris balls, as well as through the efforts of storm spotters.^{[citation needed]}

Tornado rating scales

There are several scales for rating the strength of tornadoes. The Fujita scale rates tornadoes by damage caused and has been replaced in some countries by the updated Enhanced Fujita Scale. An F0 or EF0 tornado, the weakest category, damages trees, but not substantial structures. An F5 or EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers. The similar TORRO scale ranges from T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes.^[10] Doppler radar data, photogrammetry, and ground swirl patterns (trochoidal marks) may also be analyzed to determine intensity and assign a rating.^[11][12]

Etymology

The word tornado comes from the Spanish word tornado (past participle of ‘to turn’, or ‘to have turned’, which comes from the Latin tonare ‘to thunder’.^[13][14] Tornadoes’ opposite phenomena are the widespread, straight-line derechos (, from Spanish: derecho [deˈɾetʃo], ‘straight’). A tornado is also commonly referred to as a «twister» or the old-fashioned colloquial term cyclone.^[15][16]

Definitions

A tornado is a violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud.^[17] For a vortex to be classified as a tornado, it must be in contact with both the ground and the cloud base. The term is not precisely defined; for example, there is disagreement as to whether separate touchdowns of the same funnel constitute separate tornadoes.^[5] Tornado refers to the vortex of wind, not the condensation cloud.^[18][19]

Funnel cloud

A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds (as described by Bernoulli’s principle) and rapid rotation (due to cyclostrophic balance) usually cause water vapor in the air to condense into cloud droplets due to adiabatic cooling. This results in the formation of a visible funnel cloud or condensation funnel.^[20]

There is some disagreement over the definition of a funnel cloud and a condensation funnel. According to the Glossary of Meteorology, a funnel cloud is any rotating cloud pendant from a cumulus or cumulonimbus, and thus most tornadoes are included under this definition.^[21] Among many meteorologists, the ‘funnel cloud’ term is strictly defined as a rotating cloud which is not associated with strong winds at the surface, and condensation funnel is a broad term for any rotating cloud below a cumuliform cloud.^[5]

Tornadoes often begin as funnel clouds with no associated strong winds at the surface, and not all funnel clouds evolve into tornadoes. Most tornadoes produce strong winds at the surface while the visible funnel is still above the ground, so it is difficult to discern the difference between a funnel cloud and a tornado from a distance.^[5]

Outbreaks and families

Occasionally, a single storm will produce more than one tornado, either simultaneously or in succession. Multiple tornadoes produced by the same storm cell are referred to as a «tornado family».^[22] Several tornadoes are sometimes spawned from the same large-scale storm system. If there is no break in activity, this is considered a tornado outbreak (although the term «tornado outbreak» has various definitions). A period of several successive days with tornado outbreaks in the same general area (spawned by multiple weather systems) is a tornado outbreak sequence, occasionally called an extended tornado outbreak.^[17][23][24]

Characteristics

Size and shape

Most tornadoes take on the appearance of a narrow funnel, a few hundred meters (yards) across, with a small cloud of debris near the ground. Tornadoes may be obscured completely by rain or dust. These tornadoes are especially dangerous, as even experienced meteorologists might not see them.^[25]

Small, relatively weak landspouts may be visible only as a small swirl of dust on the ground. Although the condensation funnel may not extend all the way to the ground, if associated surface winds are greater than 64 km/h (40 mph), the circulation is considered a tornado.^[18] A tornado with a nearly cylindrical profile and relatively low height is sometimes referred to as a «stovepipe» tornado. Large tornadoes which appear at least as wide as their cloud-to-ground height can look like large wedges stuck into the ground, and so are known as «wedge tornadoes» or «wedges».^[26] The «stovepipe» classification is also used for this type of tornado if it otherwise fits that profile. A wedge can be so wide that it appears to be a block of dark clouds, wider than the distance from the cloud base to the ground. Even experienced storm observers may not be able to tell the difference between a low-hanging cloud and a wedge tornado from a distance. Many, but not all major tornadoes are wedges.^[26]

Tornadoes in the dissipating stage can resemble narrow tubes or ropes, and often curl or twist into complex shapes. These tornadoes are said to be «roping out», or becoming a «rope tornado». When they rope out, the length of their funnel increases, which forces the winds within the funnel to weaken due to conservation of angular momentum.^[27] Multiple-vortex tornadoes can appear as a family of swirls circling a common center, or they may be completely obscured by condensation, dust, and debris, appearing to be a single funnel.^[28]

In the United States, tornadoes are around 500 feet (150 m) across on average.^[25] However, there is a wide range of tornado sizes. Weak tornadoes, or strong yet dissipating tornadoes, can be exceedingly narrow, sometimes only a few feet or couple meters across. One tornado was reported to have a damage path only 7 feet (2.1 m) long.^[25] On the other end of the spectrum, wedge tornadoes can have a damage path a mile (1.6 km) wide or more. A tornado that affected Hallam, Nebraska on May 22, 2004, was up to 2.5 miles (4.0 km) wide at the ground, and a tornado in El Reno, Oklahoma on May 31, 2013, was approximately 2.6 miles (4.2 km) wide, the widest on record.^[4][29]

Track length

In the United States, the average tornado travels on the ground for 5 miles (8.0 km). However, tornadoes are capable of both much shorter and much longer damage paths: one tornado was reported to have a damage path only 7 feet (2.1 m) long, while the record-holding tornado for path length—the Tri-State Tornado, which affected parts of Missouri, Illinois, and Indiana on March 18, 1925—was on the ground continuously for 219 miles (352 km).^[25] Many tornadoes which appear to have path lengths of 100 miles (160 km) or longer are composed of a family of tornadoes which have formed in quick succession; however, there is no substantial evidence that this occurred in the case of the Tri-State Tornado.^[23] In fact, modern reanalysis of the path suggests that the tornado may have begun 15 miles (24 km) further west than previously thought.^[30]

Appearance

Tornadoes can have a wide range of colors, depending on the environment in which they form. Those that form in dry environments can be nearly invisible, marked only by swirling debris at the base of the funnel. Condensation funnels that pick up little or no debris can be gray to white. While traveling over a body of water (as a waterspout), tornadoes can turn white or even blue. Slow-moving funnels, which ingest a considerable amount of debris and dirt, are usually darker, taking on the color of debris. Tornadoes in the Great Plains can turn red because of the reddish tint of the soil, and tornadoes in mountainous areas can travel over snow-covered ground, turning white.^[25]

Lighting conditions are a major factor in the appearance of a tornado. A tornado which is «back-lit» (viewed with the sun behind it) appears very dark. The same tornado, viewed with the sun at the observer’s back, may appear gray or brilliant white. Tornadoes which occur near the time of sunset can be many different colors, appearing in hues of yellow, orange, and pink.^[15][32]

Dust kicked up by the winds of the parent thunderstorm, heavy rain and hail, and the darkness of night are all factors that can reduce the visibility of tornadoes. Tornadoes occurring in these conditions are especially dangerous, since only weather radar observations, or possibly the sound of an approaching tornado, serve as any warning to those in the storm’s path. Most significant tornadoes form under the storm’s updraft base, which is rain-free,^[33] making them visible.^[34] Also, most tornadoes occur in the late afternoon, when the bright sun can penetrate even the thickest clouds.^[23]

There is mounting evidence, including Doppler on Wheels mobile radar images and eyewitness accounts, that most tornadoes have a clear, calm center with extremely low pressure, akin to the eye of tropical cyclones. Lightning is said to be the source of illumination for those who claim to have seen the interior of a tornado.^[35][36][37]

Rotation

Tornadoes normally rotate cyclonically (when viewed from above, this is counterclockwise in the northern hemisphere and clockwise in the southern). While large-scale storms always rotate cyclonically due to the Coriolis effect, thunderstorms and tornadoes are so small that the direct influence of the Coriolis effect is unimportant, as indicated by their large Rossby numbers. Supercells and tornadoes rotate cyclonically in numerical simulations even when the Coriolis effect is neglected.^[38][39] Low-level mesocyclones and tornadoes owe their rotation to complex processes within the supercell and ambient environment.^[40]

Approximately 1 percent of tornadoes rotate in an anticyclonic direction in the northern hemisphere. Typically, systems as weak as landspouts and gustnadoes can rotate anticyclonically, and usually only those which form on the anticyclonic shear side of the descending rear flank downdraft (RFD) in a cyclonic supercell.^[41] On rare occasions, anticyclonic tornadoes form in association with the mesoanticyclone of an anticyclonic supercell, in the same manner as the typical cyclonic tornado, or as a companion tornado either as a satellite tornado or associated with anticyclonic eddies within a supercell.^[42]

Sound and seismology

Tornadoes emit widely on the acoustics spectrum and the sounds are caused by multiple mechanisms. Various sounds of tornadoes have been reported, mostly related to familiar sounds for the witness and generally some variation of a whooshing roar. Popularly reported sounds include a freight train, rushing rapids or waterfall, a nearby jet engine, or combinations of these. Many tornadoes are not audible from much distance; the nature of and the propagation distance of the audible sound depends on atmospheric conditions and topography.^[5]

The winds of the tornado vortex and of constituent turbulent eddies, as well as airflow interaction with the surface and debris, contribute to the sounds. Funnel clouds also produce sounds. Funnel clouds and small tornadoes are reported as whistling, whining, humming, or the buzzing of innumerable bees or electricity, or more or less harmonic, whereas many tornadoes are reported as a continuous, deep rumbling, or an irregular sound of «noise».^[43]

Since many tornadoes are audible only when very near, sound is not to be thought of as a reliable warning signal for a tornado. Tornadoes are also not the only source of such sounds in severe thunderstorms; any strong, damaging wind, a severe hail volley, or continuous thunder in a thunderstorm may produce a roaring sound.^[44]

Tornadoes also produce identifiable inaudible infrasonic signatures.^[45]

Unlike audible signatures, tornadic signatures have been isolated; due to the long-distance propagation of low-frequency sound, efforts are ongoing to develop tornado prediction and detection devices with additional value in understanding tornado morphology, dynamics, and creation.^[46] Tornadoes also produce a detectable seismic signature, and research continues on isolating it and understanding the process.^[47]

Electromagnetic, lightning, and other effects

Tornadoes emit on the electromagnetic spectrum, with sferics and E-field effects detected.^[46][48][49] There are observed correlations between tornadoes and patterns of lightning. Tornadic storms do not contain more lightning than other storms and some tornadic cells never produce lightning at all. More often than not, overall cloud-to-ground (CG) lightning activity decreases as a tornado touches the surface and returns to the baseline level when the tornado dissipates. In many cases, intense tornadoes and thunderstorms exhibit an increased and anomalous dominance of positive polarity CG discharges.^[50] Electromagnetics and lightning have little or nothing to do directly with what drives tornadoes (tornadoes are basically a thermodynamic phenomenon), although there are likely connections with the storm and environment affecting both phenomena.^{[citation needed]}

Luminosity has been reported in the past and is probably due to misidentification of external light sources such as lightning, city lights, and power flashes from broken lines, as internal sources are now uncommonly reported and are not known to ever have been recorded. In addition to winds, tornadoes also exhibit changes in atmospheric variables such as temperature, moisture, and atmospheric pressure. For example, on June 24, 2003, near Manchester, South Dakota, a probe measured a 100-millibar (100 hPa; 3.0 inHg) pressure decrease. The pressure dropped gradually as the vortex approached then dropped extremely rapidly to 850 mbar (850 hPa; 25 inHg) in the core of the violent tornado before rising rapidly as the vortex moved away, resulting in a V-shape pressure trace. Temperature tends to decrease and moisture content to increase in the immediate vicinity of a tornado.^[51]

Life cycle

Supercell relationship

Tornadoes often develop from a class of thunderstorms known as supercells. Supercells contain mesocyclones, an area of organized rotation a few kilometers/miles up in the atmosphere, usually 1.6–9.7 km (1–6 miles) across. Most intense tornadoes (EF3 to EF5 on the Enhanced Fujita Scale) develop from supercells. In addition to tornadoes, very heavy rain, frequent lightning, strong wind gusts, and hail are common in such storms.^[52][53]

Most tornadoes from supercells follow a recognizable life cycle which begins when increasing rainfall drags with it an area of quickly descending air known as the rear flank downdraft (RFD). This downdraft accelerates as it approaches the ground, and drags the supercell’s rotating mesocyclone towards the ground with it.^[18]

Formation

As the mesocyclone lowers below the cloud base, it begins to take in cool, moist air from the downdraft region of the storm. The convergence of warm air in the updraft and cool air causes a rotating wall cloud to form. The RFD also focuses the mesocyclone’s base, causing it to draw air from a smaller and smaller area on the ground. As the updraft intensifies, it creates an area of low pressure at the surface. This pulls the focused mesocyclone down, in the form of a visible condensation funnel. As the funnel descends, the RFD also reaches the ground, fanning outward and creating a gust front that can cause severe damage a considerable distance from the tornado. Usually, the funnel cloud begins causing damage on the ground (becoming a tornado) within a few minutes of the RFD reaching the ground.^[18][54] Many other aspects of tornado formation (such as why some storms form tornadoes while others do not, or what precise role downdrafts, temperature, and moisture play in tornado formation) are still poorly understood.^[55]

Maturity

Initially, the tornado has a good source of warm, moist air flowing inward to power it, and it grows until it reaches the «mature stage». This can last from a few minutes to more than an hour, and during that time a tornado often causes the most damage, and in rare cases can be more than 1.6 km (1 mile) across. The low pressured atmosphere at the base of the tornado is essential to the endurance of the system.^[56] Meanwhile, the RFD, now an area of cool surface winds, begins to wrap around the tornado, cutting off the inflow of warm air which previously fed the tornado.^[18]
The flow inside the funnel of the tornado is downward, supplying water vapor from the cloud above. This is contrary to the upward flow inside hurricanes, supplying water vapor from the warm ocean below. Therefore, the energy of the tornado is supplied from the cloud above. The complicated mechanism is explained in
^[57]
[58]

Dissipation

As the RFD completely wraps around and chokes off the tornado’s air supply, the vortex begins to weaken, becoming thin and rope-like. This is the «dissipating stage», often lasting no more than a few minutes, after which the tornado ends. During this stage, the shape of the tornado becomes highly influenced by the winds of the parent storm, and can be blown into fantastic patterns.^[23][31][32] Even though the tornado is dissipating, it is still capable of causing damage. The storm is contracting into a rope-like tube and, due to conservation of angular momentum, winds can increase at this point.^[27]

As the tornado enters the dissipating stage, its associated mesocyclone often weakens as well, as the rear flank downdraft cuts off the inflow powering it. Sometimes, in intense supercells, tornadoes can develop cyclically. As the first mesocyclone and associated tornado dissipate, the storm’s inflow may be concentrated into a new area closer to the center of the storm and possibly feed a new mesocyclone. If a new mesocyclone develops, the cycle may start again, producing one or more new tornadoes. Occasionally, the old (occluded) mesocyclone and the new mesocyclone produce a tornado at the same time.^{[citation needed]}

Although this is a widely accepted theory for how most tornadoes form, live, and die, it does not explain the formation of smaller tornadoes, such as landspouts, long-lived tornadoes, or tornadoes with multiple vortices. These each have different mechanisms which influence their development—however, most tornadoes follow a pattern similar to this one.^[59]

Types

Multiple vortex

A multiple-vortex tornado is a type of tornado in which two or more columns of spinning air rotate about their own axes and at the same time revolve around a common center. A multi-vortex structure can occur in almost any circulation, but is very often observed in intense tornadoes. These vortices often create small areas of heavier damage along the main tornado path.^[5][18] This is a phenomenon that is distinct from a satellite tornado, which is a smaller tornado that forms very near a large, strong tornado contained within the same mesocyclone. The satellite tornado may appear to «orbit» the larger tornado (hence the name), giving the appearance of one, large multi-vortex tornado. However, a satellite tornado is a distinct circulation, and is much smaller than the main funnel.^[5]

Waterspout

A waterspout is defined by the National Weather Service as a tornado over water. However, researchers typically distinguish «fair weather» waterspouts from tornadic (i.e. associated with a mesocyclone) waterspouts. Fair weather waterspouts are less severe but far more common, and are similar to dust devils and landspouts. They form at the bases of cumulus congestus clouds over tropical and subtropical waters. They have relatively weak winds, smooth laminar walls, and typically travel very slowly. They occur most commonly in the Florida Keys and in the northern Adriatic Sea.^[60][61][62] In contrast, tornadic waterspouts are stronger tornadoes over water. They form over water similarly to mesocyclonic tornadoes, or are stronger tornadoes which cross over water. Since they form from severe thunderstorms and can be far more intense, faster, and longer-lived than fair weather waterspouts, they are more dangerous.^[63] In official tornado statistics, waterspouts are generally not counted unless they affect land, though some European weather agencies count waterspouts and tornadoes together.^[5][64]

Landspout

A landspout, or dust-tube tornado, is a tornado not associated with a mesocyclone. The name stems from their characterization as a «fair weather waterspout on land». Waterspouts and landspouts share many defining characteristics, including relative weakness, short lifespan, and a small, smooth condensation funnel that often does not reach the surface. Landspouts also create a distinctively laminar cloud of dust when they make contact with the ground, due to their differing mechanics from true mesoform tornadoes. Though usually weaker than classic tornadoes, they can produce strong winds which could cause serious damage.^[5][18]

Similar circulations

Gustnado

A gustnado, or gust front tornado, is a small, vertical swirl associated with a gust front or downburst. Because they are not connected with a cloud base, there is some debate as to whether or not gustnadoes are tornadoes. They are formed when fast-moving cold, dry outflow air from a thunderstorm is blown through a mass of stationary, warm, moist air near the outflow boundary, resulting in a «rolling» effect (often exemplified through a roll cloud). If low level wind shear is strong enough, the rotation can be turned vertically or diagonally and make contact with the ground. The result is a gustnado.^[5][65] They usually cause small areas of heavier rotational wind damage among areas of straight-line wind damage.^{[citation needed]}

Dust devil

A dust devil (also known as a whirlwind) resembles a tornado in that it is a vertical swirling column of air. However, they form under clear skies and are no stronger than the weakest tornadoes. They form when a strong convective updraft is formed near the ground on a hot day. If there is enough low-level wind shear, the column of hot, rising air can develop a small cyclonic motion that can be seen near the ground. They are not considered tornadoes because they form during fair weather and are not associated with any clouds. However, they can, on occasion, result in major damage.^[25][66]

Fire whirls

Small-scale, tornado-like circulations can occur near any intense surface heat source. Those that occur near intense wildfires are called fire whirls. They are not considered tornadoes, except in the rare case where they connect to a pyrocumulus or other cumuliform cloud above. Fire whirls usually are not as strong as tornadoes associated with thunderstorms. They can, however, produce significant damage.^[23]

Steam devils

A steam devil is a rotating updraft between 50-and-200-metre wide (160 and 660 ft) that involves steam or smoke. These formations do not involve high wind speeds, only completing a few rotations per minute. Steam devils are very rare. They most often form from smoke issuing from a power plant’s smokestack. Hot springs and deserts may also be suitable locations for a tighter, faster-rotating steam devil to form. The phenomenon can occur over water, when cold arctic air passes over relatively warm water.^[25]

Intensity and damage

Tornado rating classifications^[23][67]

F0 EF0	F1 EF1	F2 EF2	F3 EF3	F4 EF4	F5 EF5
Weak	Strong	Violent
	Significant
	Intense

The Fujita scale and the Enhanced Fujita Scale rate tornadoes by damage caused. The Enhanced Fujita (EF) Scale was an update to the older Fujita scale, by expert elicitation, using engineered wind estimates and better damage descriptions. The EF Scale was designed so that a tornado rated on the Fujita scale would receive the same numerical rating, and was implemented starting in the United States in 2007. An EF0 tornado will probably damage trees but not substantial structures, whereas an EF5 tornado can rip buildings off their foundations leaving them bare and even deform large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler weather radar data, photogrammetry, and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and award a rating.^[5][68][69]

Tornadoes vary in intensity regardless of shape, size, and location, though strong tornadoes are typically larger than weak tornadoes. The association with track length and duration also varies, although longer track tornadoes tend to be stronger.^[70] In the case of violent tornadoes, only a small portion of the path is of violent intensity, most of the higher intensity from subvortices.^[23]

In the United States, 80% of tornadoes are EF0 and EF1 (T0 through T3) tornadoes. The rate of occurrence drops off quickly with increasing strength—less than 1% are violent tornadoes (EF4, T8 or stronger).^[71] Current records may significantly underestimate the frequency of strong (EF2-EF3) and violent (EF4-EF5) tornadoes, as damage-based intensity estimates are limited to structures and vegetation that a tornado impacts. A tornado may be much stronger than its damage-based rating indicates if its strongest winds occur away from suitable damage indicators, such as in an open field.^[72][73] Outside Tornado Alley, and North America in general, violent tornadoes are extremely rare. This is apparently mostly due to the lesser number of tornadoes overall, as research shows that tornado intensity distributions are fairly similar worldwide. A few significant tornadoes occur annually in Europe, Asia, southern Africa, and southeastern South America.^[74]

Climatology

The United States has the most tornadoes of any country, nearly four times more than estimated in all of Europe, excluding waterspouts.^[75] This is mostly due to the unique geography of the continent. North America is a large continent that extends from the tropics north into arctic areas, and has no major east–west mountain range to block air flow between these two areas. In the middle latitudes, where most tornadoes of the world occur, the Rocky Mountains block moisture and buckle the atmospheric flow, forcing drier air at mid-levels of the troposphere due to downsloped winds, and causing the formation of a low pressure area downwind to the east of the mountains. Increased westerly flow off the Rockies force the formation of a dry line when the flow aloft is strong,^[76] while the Gulf of Mexico fuels abundant low-level moisture in the southerly flow to its east. This unique topography allows for frequent collisions of warm and cold air, the conditions that breed strong, long-lived storms throughout the year. A large portion of these tornadoes form in an area of the central United States known as Tornado Alley.^[77] This area extends into Canada, particularly Ontario and the Prairie Provinces, although southeast Quebec, the interior of British Columbia, and western New Brunswick are also tornado-prone.^[78] Tornadoes also occur across northeastern Mexico.^[5]

The United States averages about 1,200 tornadoes per year, followed by Canada, averaging 62 reported per year.^[79] NOAA’s has a higher average 100 per year in Canada.^[80] The Netherlands has the highest average number of recorded tornadoes per area of any country (more than 20, or 0.00048/km², 0.0012/sq mi annually), followed by the UK (around 33, 0.00013/km², 0.00034/sq mi per year), although those are of lower intensity, briefer^[81][82] and cause minor damage.^[75]

Tornadoes kill an average of 179 people per year in Bangladesh, the most in the world.^[83] Reasons for this include the region’s high population density, poor construction quality, and lack of tornado safety knowledge.^[83][84] Other areas of the world that have frequent tornadoes include South Africa, the La Plata Basin area, portions of Europe, Australia and New Zealand, and far eastern Asia.^[8][85]

Tornadoes are most common in spring and least common in winter, but tornadoes can occur any time of year that favorable conditions occur.^[23] Spring and fall experience peaks of activity as those are the seasons when stronger winds, wind shear, and atmospheric instability are present.^[86] Tornadoes are focused in the right front quadrant of landfalling tropical cyclones, which tend to occur in the late summer and autumn. Tornadoes can also be spawned as a result of eyewall mesovortices, which persist until landfall.^[87]

Tornado occurrence is highly dependent on the time of day, because of solar heating.^[88] Worldwide, most tornadoes occur in the late afternoon, between 15:00 (3 pm) and 19:00 (7 pm) local time, with a peak near 17:00 (5 pm).^{[89][90][91][92][93]} Destructive tornadoes can occur at any time of day. The Gainesville Tornado of 1936, one of the deadliest tornadoes in history, occurred at 8:30 am local time.^[23]

The United Kingdom has the highest incidence of tornadoes per unit area of land in the world.^[94] Unsettled conditions and weather fronts transverse the British Isles at all times of the years, and are responsible for spawning the tornadoes, which consequently form at all times of the year. The United Kingdom has at least 34 tornadoes per year and possibly as many as 50.^[95] Most tornadoes in the United Kingdom are weak, but they are occasionally destructive. For example, the Birmingham tornado of 2005 and the London tornado of 2006 both registered F2 on the Fujita scale and both caused significant damage and injury.^[96]

Associations with climate and climate change

Associations with various climate and environmental trends exist. For example, an increase in the sea surface temperature of a source region (e.g. Gulf of Mexico and Mediterranean Sea) increases atmospheric moisture content. Increased moisture can fuel an increase in severe weather and tornado activity, particularly in the cool season.^[97]

Some evidence does suggest that the Southern Oscillation is weakly correlated with changes in tornado activity, which vary by season and region, as well as whether the ENSO phase is that of El Niño or La Niña.^[98] Research has found that fewer tornadoes and hailstorms occur in winter and spring in the U.S. central and southern plains during El Niño, and more occur during La Niña, than in years when temperatures in the Pacific are relatively stable. Ocean conditions could be used to forecast extreme spring storm events several months in advance.^[99]

Climatic shifts may affect tornadoes via teleconnections in shifting the jet stream and the larger weather patterns. The climate-tornado link is confounded by the forces affecting larger patterns and by the local, nuanced nature of tornadoes. Although it is reasonable to suspect that global warming may affect trends in tornado activity,^[100] any such effect is not yet identifiable due to the complexity, local nature of the storms, and database quality issues. Any effect would vary by region.^[101]

Detection

Rigorous attempts to warn of tornadoes began in the United States in the mid-20th century. Before the 1950s, the only method of detecting a tornado was by someone seeing it on the ground. Often, news of a tornado would reach a local weather office after the storm. However, with the advent of weather radar, areas near a local office could get advance warning of severe weather. The first public tornado warnings were issued in 1950 and the first tornado watches and convective outlooks came about in 1952. In 1953, it was confirmed that hook echoes were associated with tornadoes.^[102] By recognizing these radar signatures, meteorologists could detect thunderstorms probably producing tornadoes from several miles away.^[103]

Radar

Today most developed countries have a network of weather radars, which serves as the primary method of detecting hook signatures that are likely associated with tornadoes. In the United States and a few other countries, Doppler weather radar stations are used. These devices measure the velocity and radial direction (towards or away from the radar) of the winds within a storm, and so can spot evidence of rotation in storms from over 160 km (100 miles) away. When storms are distant from a radar, only areas high within the storm are observed and the important areas below are not sampled.^[104] Data resolution also decreases with distance from the radar. Some meteorological situations leading to tornadogenesis are not readily detectable by radar and tornado development may occasionally take place more quickly than radar can complete a scan and send the batch of data. Doppler radar systems can detect mesocyclones within a supercell thunderstorm. This allows meteorologists to predict tornado formations throughout thunderstorms.^[105]

Storm spotting

In the mid-1970s, the U.S. National Weather Service (NWS) increased its efforts to train storm spotters so they could spot key features of storms that indicate severe hail, damaging winds, and tornadoes, as well as storm damage and flash flooding. The program was called Skywarn, and the spotters were local sheriff’s deputies, state troopers, firefighters, ambulance drivers, amateur radio operators, civil defense (now emergency management) spotters, storm chasers, and ordinary citizens. When severe weather is anticipated, local weather service offices request these spotters to look out for severe weather and report any tornadoes immediately, so that the office can warn of the hazard.^{[citation needed]}

Spotters usually are trained by the NWS on behalf of their respective organizations, and report to them. The organizations activate public warning systems such as sirens and the Emergency Alert System (EAS), and they forward the report to the NWS.^[106]
There are more than 230,000 trained Skywarn weather spotters across the United States.^[107]

In Canada, a similar network of volunteer weather watchers, called Canwarn, helps spot severe weather, with more than 1,000 volunteers.^[108] In Europe, several nations are organizing spotter networks under the auspices of Skywarn Europe^[109] and the Tornado and Storm Research Organisation (TORRO) has maintained a network of spotters in the United Kingdom since 1974.^[110]

Storm spotters are required because radar systems such as NEXRAD detect signatures that suggest the presence of tornadoes, rather than tornadoes as such.^[111] Radar may give a warning before there is any visual evidence of a tornado or an imminent one, but ground truth from an observer can give definitive information.^[112] The spotter’s ability to see what radar cannot is especially important as distance from the radar site increases, because the radar beam becomes progressively higher in altitude further away from the radar, chiefly due to curvature of Earth, and the beam also spreads out.^[104]

Visual evidence

Storm spotters are trained to discern whether or not a storm seen from a distance is a supercell. They typically look to its rear, the main region of updraft and inflow. Under that updraft is a rain-free base, and the next step of tornadogenesis is the formation of a rotating wall cloud. The vast majority of intense tornadoes occur with a wall cloud on the backside of a supercell.^[71]

Evidence of a supercell is based on the storm’s shape and structure, and cloud tower features such as a hard and vigorous updraft tower, a persistent, large overshooting top, a hard anvil (especially when backsheared against strong upper level winds), and a corkscrew look or striations. Under the storm and closer to where most tornadoes are found, evidence of a supercell and the likelihood of a tornado includes inflow bands (particularly when curved) such as a «beaver tail», and other clues such as strength of inflow, warmth and moistness of inflow air, how outflow- or inflow-dominant a storm appears, and how far is the front flank precipitation core from the wall cloud. Tornadogenesis is most likely at the interface of the updraft and rear flank downdraft, and requires a balance between the outflow and inflow.^[18]

Only wall clouds that rotate spawn tornadoes, and they usually precede the tornado between five and thirty minutes. Rotating wall clouds may be a visual manifestation of a low-level mesocyclone. Barring a low-level boundary, tornadogenesis is highly unlikely unless a rear flank downdraft occurs, which is usually visibly evidenced by evaporation of cloud adjacent to a corner of a wall cloud. A tornado often occurs as this happens or shortly afterwards; first, a funnel cloud dips and in nearly all cases by the time it reaches halfway down, a surface swirl has already developed, signifying a tornado is on the ground before condensation connects the surface circulation to the storm. Tornadoes may also develop without wall clouds, under flanking lines and on the leading edge. Spotters watch all areas of a storm, and the cloud base and surface.^[113]

Extremes

The tornado which holds most records in history was the Tri-State Tornado, which roared through parts of Missouri, Illinois, and Indiana on March 18, 1925. It was likely an F5, though tornadoes were not ranked on any scale in that era. It holds records for longest path length (219 miles; 352 km), longest duration (about 3.5 hours), and fastest forward speed for a significant tornado (73 mph; 117 km/h) anywhere on Earth. In addition, it is the deadliest single tornado in United States history (695 dead).^[23] The tornado was also the costliest tornado in history at the time (unadjusted for inflation), but in the years since has been surpassed by several others if population changes over time are not considered. When costs are normalized for wealth and inflation, it ranks third today.^[114]

The deadliest tornado in world history was the Daultipur-Salturia Tornado in Bangladesh on April 26, 1989, which killed approximately 1,300 people.^[83]Bangladesh has had at least 19 tornadoes in its history that killed more than 100 people, almost half of the total in the rest of the world.^{[citation needed]}

One of the most extensive tornado outbreaks on record was the 1974 Super Outbreak, which affected a large area of the central United States and extreme southern Ontario on April 3 and 4, 1974. The outbreak featured 148 tornadoes in 18 hours, many of which were violent; six were of F5 intensity, and twenty-four peaked at F4 strength. Sixteen tornadoes were on the ground at the same time during its peak. More than 300 people, possibly as many as 330, were killed.^[115]

While direct measurement of the most violent tornado wind speeds is nearly impossible, since conventional anemometers would be destroyed by the intense winds and flying debris, some tornadoes have been scanned by mobile Doppler radar units, which can provide a good estimate of the tornado’s winds. The highest wind speed ever measured in a tornado, which is also the highest wind speed ever recorded on the planet, is 301 ± 20 mph (484 ± 32 km/h) in the F5 Bridge Creek-Moore, Oklahoma, tornado which killed 36 people.^[116] The reading was taken about 100 feet (30 m) above the ground.^[3]

Storms that produce tornadoes can feature intense updrafts, sometimes exceeding 150 mph (240 km/h). Debris from a tornado can be lofted into the parent storm and carried a very long distance. A tornado which affected Great Bend, Kansas, in November 1915, was an extreme case, where a «rain of debris» occurred 80 miles (130 km) from the town, a sack of flour was found 110 miles (180 km) away, and a cancelled check from the Great Bend bank was found in a field outside of Palmyra, Nebraska, 305 miles (491 km) to the northeast.^[117] Waterspouts and tornadoes have been advanced as an explanation for instances of raining fish and other animals.^[118]

Safety

Though tornadoes can strike in an instant, there are precautions and preventative measures that can be taken to increase the chances of survival. Authorities such as the Storm Prediction Center in the United States advise having a pre-determined plan should a tornado warning be issued. When a warning is issued, going to a basement or an interior first-floor room of a sturdy building greatly increases chances of survival.^[119] In tornado-prone areas, many buildings have underground storm cellars, which have saved thousands of lives.^[120]

Some countries have meteorological agencies which distribute tornado forecasts and increase levels of alert of a possible tornado (such as tornado watches and warnings in the United States and Canada). Weather radios provide an alarm when a severe weather advisory is issued for the local area, mainly available only in the United States. Unless the tornado is far away and highly visible, meteorologists advise that drivers park their vehicles far to the side of the road (so as not to block emergency traffic), and find a sturdy shelter. If no sturdy shelter is nearby, getting low in a ditch is the next best option. Highway overpasses are one of the worst places to take shelter during tornadoes, as the constricted space can be subject to increased wind speed and funneling of debris underneath the overpass.^[121]

Myths and misconceptions

Folklore often identifies a green sky with tornadoes, and though the phenomenon may be associated with severe weather, there is no evidence linking it specifically with tornadoes.^[122] It is often thought that opening windows will lessen the damage caused by the tornado. While there is a large drop in atmospheric pressure inside a strong tornado, the pressure difference is unlikely to cause significant damage. Opening windows may instead increase the severity of the tornado’s damage.^[123] A violent tornado can destroy a house whether its windows are open or closed.^[123][124]

Another commonly held misconception is that highway overpasses provide adequate shelter from tornadoes. This belief is partly inspired by widely circulated video captured during the 1991 tornado outbreak near Andover, Kansas, where a news crew and several other people took shelter under an overpass on the Kansas Turnpike and safely rode out a tornado as it passed nearby.^[125] However, a highway overpass is a dangerous place during a tornado, and the subjects of the video remained safe due to an unlikely combination of events: the storm in question was a weak tornado, the tornado did not directly strike the overpass,^[125] and the overpass itself was of a unique design. Due to the Venturi effect, tornadic winds are accelerated in the confined space of an overpass.^[126] Indeed, in the 1999 Oklahoma tornado outbreak of May 3, 1999, three highway overpasses were directly struck by tornadoes, and at each of the three locations there was a fatality, along with many life-threatening injuries.^[127] By comparison, during the same tornado outbreak, more than 2,000 homes were completely destroyed and another 7,000 damaged, and yet only a few dozen people died in their homes.^[121]

An old belief is that the southwest corner of a basement provides the most protection during a tornado. The safest place is the side or corner of an underground room opposite the tornado’s direction of approach (usually the northeast corner), or the central-most room on the lowest floor. Taking shelter in a basement, under a staircase, or under a sturdy piece of furniture such as a workbench further increases the chances of survival.^[123][124]

There are areas which people believe to be protected from tornadoes, whether by being in a city, near a major river, hill, or mountain, or even protected by supernatural forces.^[128] Tornadoes have been known to cross major rivers, climb mountains,^[129] affect valleys, and have damaged several city centers. As a general rule, no area is safe from tornadoes, though some areas are more susceptible than others.^{[25][123][124]}

Ongoing research

Meteorology is a relatively young science and the study of tornadoes is newer still. Although researched for about 140 years and intensively for around 60 years, there are still aspects of tornadoes which remain a mystery.^[130] Meteorologists have a fairly good understanding of the development of thunderstorms and mesocyclones,^[131][132] and the meteorological conditions conducive to their formation. However, the step from supercell, or other respective formative processes, to tornadogenesis and the prediction of tornadic vs. non-tornadic mesocyclones is not yet well known and is the focus of much research.^[86]

Also under study are the low-level mesocyclone and the stretching of low-level vorticity which tightens into a tornado,^[86] in particular, what are the processes and what is the relationship of the environment and the convective storm. Intense tornadoes have been observed forming simultaneously with a mesocyclone aloft (rather than succeeding mesocyclogenesis) and some intense tornadoes have occurred without a mid-level mesocyclone.^[133]

In particular, the role of downdrafts, particularly the rear-flank downdraft, and the role of baroclinic boundaries, are intense areas of study.^[134]

Reliably predicting tornado intensity and longevity remains a problem, as do details affecting characteristics of a tornado during its life cycle and tornadolysis. Other rich areas of research are tornadoes associated with mesovortices within linear thunderstorm structures and within tropical cyclones.^[135]

Meteorologists still do not know the exact mechanisms by which most tornadoes form, and occasional tornadoes still strike without a tornado warning being issued.^[136] Analysis of observations including both stationary and mobile (surface and aerial) in-situ and remote sensing (passive and active) instruments generates new ideas and refines existing notions. Numerical modeling also provides new insights as observations and new discoveries are integrated into our physical understanding and then tested in computer simulations which validate new notions as well as produce entirely new theoretical findings, many of which are otherwise unattainable. Importantly, development of new observation technologies and installation of finer spatial and temporal resolution observation networks have aided increased understanding and better predictions.^[137]

Research programs, including field projects such as the VORTEX projects (Verification of the Origins of Rotation in Tornadoes Experiment), deployment of TOTO (the TOtable Tornado Observatory), Doppler on Wheels (DOW), and dozens of other programs, hope to solve many questions that still plague meteorologists.^[46] Universities, government agencies such as the National Severe Storms Laboratory, private-sector meteorologists, and the National Center for Atmospheric Research are some of the organizations very active in research; with various sources of funding, both private and public, a chief entity being the National Science Foundation.^[111][138] The pace of research is partly constrained by the number of observations that can be taken; gaps in information about the wind, pressure, and moisture content throughout the local atmosphere; and the computing power available for simulation.^[139]

Solar storms similar to tornadoes have been recorded, but it is unknown how closely related they are to their terrestrial counterparts.^[140]

Gallery

• 

  F0 tornado in its final stages over the North Sea near Vrångö, Sweden on July 17, 2011.

See also

References

Further reading

• Bluestein, Howard B. (1999). Tornado Alley: Monster Storms of the Great Plains. New York: Oxford University Press. ISBN 0-19-510552-4.
• Bradford, Marlene (2001). Scanning the Skies: A History of Tornado Forecasting. Norman, OK: University of Oklahoma Press. ISBN 0-8061-3302-3.
• Grazulis, Thomas P. (January 1997). Significant Tornadoes Update, 1992–1995. St. Johnsbury, VT: Environmental Films. ISBN 1-879362-04-X.
• Pybus, Nani (Spring 2016). «‘Cyclone’ Jones: Dr. Herbert L. Jones and the Origins of Tornado Research in Oklahoma». Chronicles of Oklahoma. 94: 4–31. Retrieved May 5, 2022. Heavily illustrated.

External links

• NOAA Storm Events Database 1950–present
• European Severe Weather Database
• Tornado Detection and Warnings
• Electronic Journal of Severe Storms Meteorology
• NOAA Tornado Preparedness Guide
• Tornado History Project – Maps and statistics from 1950 to present
• Physics Today What we know and don’t know about Tornadoes September 2014
• U.S. Billion-dollar Weather and Climate Disasters

Tornadoes are powerful types of storms that can occur almost anywhere when conditions are right. Have you ever wondered where tornadoes come from and how they form?

Not all tornadoes are the same, each differing in size and strength. Find out more about these monstrous swirling storms in this complete guide on tornadoes!

A tornado is a violent atmospheric storm made of strong winds. Columns of air rotate down to the ground from a thunderstorm, forming a funnel shape. 

Collections of debris, dust, and water allow us to see the rotating winds of a tornado.

A tornado is made up of released energy in thunderstorms, creating powerful winds. There are several different types of tornadoes that have their own characteristics. Some tornadoes can be minor, while others can cause hefty damage.

Why Is It Called a Tornado?

What Do Tornadoes Look Like?

Tornadoes can look different depending on what type of tornado it is. Tornadoes are accompanied by dark storm clouds. These clouds form a swirling funnel that drops down.

The larger end of the funnel is in the thunderstorm cloud. The funnel usually gets skinnier towards the end that touches the ground. The part of the tornado touching the ground can be really skinny or almost as wide as the top.

How Tall are Tornadoes?

Tornadoes can be anywhere around 5 to 10 miles (8-16 km) tall. This range could depend on the distance between the ground and the thunderstorm cloud.

The funnel of a tornado can range in size. Some may be a few hundred meters wide, while others are much larger. The tip that touches the ground is usually skinnier than the top. But some tips of tornadoes can be over a mile wide.

How Fast Do Tornadoes Move?

There are two different speeds to consider when discussing how fast a tornado is moving. 

The speed of a tornado can be measured by how fast it’s moving along its path. Speed can also be determined by how fast the rotating winds of a tornado are moving.

When referring to how fast a tornado moves in its path, it can reach up to 60 mph (97 kph) or more. A tornado can also move very slowly to the point where it may not even look like it’s moving.

Wind speeds in a tornado can reach over 200 mph (322 kph). Tornado strength is determined by wind speeds and damage caused to anything in its general path. 

Strong tornadoes that do the most damage typically have wind speeds over 200 mph (322 kph). Weaker tornadoes can have wind speeds under 80 mph (129 kph).

How Long Do Tornadoes Last?

Tornadoes can be very short-lived or have longer ground time. Most don’t last more than 20 minutes, with the average range being 5 to 10 minutes.

Some can last more than an hour long if it has the strength and resources to do so. However, these strong tornadoes are rare.

How Much Damage Can a Tornado Do?

Tornadoes have different strength ratings depending on how much damage it causes. A tornado’s wind speed can be estimated by assessing the damage.

Tornadoes can rip up houses, trees, and anything in their path. They can cause immense damage if it builds up enough speed and wind power.

Some tornadoes may last longer than others. Tornadoes that aren’t as strong and don’t last long typically cause less damage. The National Weather Service uses the Enhanced Fujita Scale to assess tornado strength.

The rating system includes damage indicators. It allow experts to determine the wind speed rating of a tornado. Damage indicators include different types of infrastructure and trees. Experts will call tornadoes by their “F Number.” The F Number goes from 0 to 5, with 5 being the strongest.

The rating system measures how fast a tornado travels and wind gust speeds. 

An F5 tornado, for example, has wind speeds between 260 and 318 mph (418 and 311 kph). F5 tornadoes can be extremely destructive. They have the ability to cause millions to billions of dollars in damage. They’re able to destroy concrete buildings and other solid infrastructure.

Weak tornadoes usually can’t damage buildings made of stronger materials. They can still cause damage to trees and homes.

Tornadoes can also cause indirect damage. Objects and debris picked up by strong tornadoes can be thrown elsewhere and damage other things in the process.

What Causes a Tornado

There are a few elements that go into what causes a tornado. Conditions like thunderstorms, warm and moist air, and air instability are the main ingredients that cause tornadoes.

In most cases, tornadoes cannot form without a thunderstorm. So the initial cause of a tornado is a thunderstorm with the right conditions to create a funnel cloud and tornado. Most thunderstorms don’t cause tornadoes, but it’s possible if all the components are there to make one.

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How Do Tornadoes Form?

Scientists are still studying how tornadoes form to better understand them. There are a few different ways a tornado can form. In almost all tornado events, a thunderstorm is needed for a tornado to form.

There are two types of thunderstorms that form tornadoes. These include supercell and non-supercell thunderstorms. The type of thunderstorm also determines what kind of tornado could form.

Tornadoes form most often from supercell thunderstorms. A combination of moist, humid air that’s unstable with differing wind directions can create a tornado.

Winds lower to the ground can be moving in one direction. Meanwhile, winds higher up move in a different direction. This process is called wind shear. 

The movement of cold air falling downward and humid air rising creates unstable air movement that begins to spin. The rising of the humid, moist, and rotating air is known as an updraft.

The direction of the air starts out by moving horizontally in the thunderstorm cloud. But when it begins moving vertically, it can create a funnel cloud. It’s not considered a tornado until it touches down on the ground. Otherwise, it stays a funnel cloud.

How Do You Spot a Tornado Before It Starts?

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What Stops a Tornado?

The only thing that can stop a tornado is itself. Just as a tornado needs energy and resources to occur, it also needs them to maintain itself.

Tornadoes can happen very fast, but they can’t be stopped by a building, even if it’s super tall or made of concrete. As less air movement occurs, tornadoes begin to slow down. The continuous movement of humid air up and cold air down can cause tornadoes to go on for longer periods.

When a tornado loses its momentum, the tip will no longer be on the ground. Rotating air currents stabilize, and the tornado eventually disappears.

Types of Tornadoes

Each type of tornado falls under the supercell and non-supercell thunderstorm categories. Two types of non-supercell tornadoes include landspouts and waterspouts.

Other types of tornadoes form from a supercell thunderstorm, such as:

• Rope tornadoes
• Cone tornadoes
• Wedge tornadoes
• Multi-vortex tornadoes

Landspouts and waterspouts are weaker tornadoes. They usually don’t last as long as the others.

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Historical Tornadoes

Tornadoes can be strong, disastrous event. There are some tornado events that break historical records for their power, speed, and damage caused.

Tri-State Tornado

One of the deadliest tornadoes was the Tri-State Tornado of 1925. This tornado event occurred across three different states and caused damage to 13 counties. It went through the southern portions of Missouri, Illinois, and Indiana on March 18, 1925.

The Tri-State Tornado traveled 219 miles and had a width of almost one mile (1.6 km). It was graded as an F5 on the Fujita Scale. It traveled slightly over 60 mph (96.5 kph) and had wind speeds exceeding 300 mph (483 kph).

Great Plains Tornado Outbreak of 1999

Multi-vortex tornadoes occurred on May 3, 1999 in Oklahoma and Kansas. There were 74 tornadoes reported in the states within a 24-hour period.

The strongest tornado in the event reached record-breaking wind speeds over 300 mph (483 kph). It was rated as an F5 tornado.

Over 8,000 homes were damaged, and more than 800 people were injured, with 46 deaths.

March 2, 2012, Tornado Outbreak

On March 2, 2012, a devastating tornado outbreak occurred in 11 different states. There were 81 tornadoes present during this event, 18 of which were in Kentucky alone.

The tornado gained enough power and speed to be graded as an EF-4, the second-highest tornado ranking. Hail was also present from severe thunderstorms surrounding the affected areas. 

There were more than 270 tornado warnings issued, and the event caused over $1.5 billion in damages. 41 people died as a result of the disastrous event.

Cyclone vs. Tornado: What’s the Difference?

Tornadoes are often referred to as cyclones, but they are different types of weather events. Tornadoes are considered small-scale cyclonic events.

Cyclones are large-scale rotating circulations in low atmospheric pressure and severe weather.

Winds circulate around low pressure during a cyclone. Tornadoes do the same, but they’re much smaller. Cyclones are more closely associated with hurricanes.

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Tornado vs. Hurricane: What’s the Difference?

A hurricane is a type of tropical storm that forms over the ocean. They’re often referred to as tropical cyclones. These weather events usually start over tropical or subtropical waters, where they build up power and wind speeds.

The maximum wind speed for a tropical storm to be classified as a hurricane is 74 mph (119 kph). When they hit land, they begin to lose power.

Hurricanes, tropical cyclones, and typhoons are the same things, but they’re referred to differently depending on where you are.

Tornado Myths & Misconceptions

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Tornado Facts

👉🏼 Tornadoes Occur Most in Spring and Summer

Tornadoes can occur any time of the year under the right conditions. However, they mostly occur during the spring and summer. This is because tornadoes need moisture and warm air to form.

👉🏼 Tornadoes Don’t Usually Make Deep Trenches

You may have seen movies where tornadoes plow through the ground, creating trenches. Although it’s possible and has happened before, it’s not a common occurrence.

Tornado FAQs

Last Updated:
26 Mar 2023
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A tornado is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. They are often referred to as a twister or a cyclone,^[1] although the word cyclone is used in meteorology in a wider sense, to name any closed low pressure circulation. Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust. Most tornadoes have wind speeds less than 110 miles per hour (177 km/h), are approximately 250 feet (80 m) across, and travel a few miles (several kilometers) before dissipating. The most extreme tornadoes can attain wind speeds of more than 300 mph (480 km/h), stretch more than two miles (3 km) across, and stay on the ground for dozens of miles (more than 100 km).^[2][3][4]

Various types of tornadoes include the landspout, multiple vortex tornado, and waterspout. Waterspouts are characterized by a spiraling funnel-shaped wind current, connecting to a large cumulus or cumulonimbus cloud. They are generally classified as non-supercellular tornadoes that develop over bodies of water.^[5] These spiraling columns of air frequently develop in tropical areas close to the equator, and are less common at high latitudes.^[6] Other tornado-like phenomena that exist in nature include the gustnado, dust devil, fire whirls, and steam devil.

Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes in the world occur in the Tornado Alley region of the United States, although they can occur nearly anywhere in North America.^[7] They also occasionally occur in south-central and eastern Asia, the Philippines, south east Asia, like Malaysia,^[8] northern and east-central South America, Southern Africa, northwestern and southeast Europe, western and southeastern Australia, and New Zealand.^[9] Tornadoes can be detected before or as they occur through the use of Pulse-Doppler radar by recognizing patterns in velocity and reflectivity data, such as hook echoes, as well as by the efforts of storm spotters.

There are several different scales for rating the strength of tornadoes. The Fujita scale rates tornadoes by damage caused, and has been replaced in some countries by the updated Enhanced Fujita Scale. An F0 or EF0 tornado, the weakest category, damages trees, but not substantial structures. An F5 or EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes.^[10] Doppler radar data, photogrammetry, and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and assign a rating.^[11]

Etymology

The word tornado is an altered form of the Spanish word tronada, which means «thunderstorm». This in turn was taken from the Latin tonare, meaning «to thunder». It most likely reached its present form through a combination of the Spanish tronada and tornar («to turn»); however, this may be a folk etymology.^[12][13] A tornado is also commonly referred to as a «twister», and is also sometimes referred to by the old-fashioned colloquial term cyclone.^[14][15] The term «cyclone» is used as a synonym for «tornado» in the often-aired 1939 film, The Wizard of Oz. The term «twister» is also used in that film, along with being the title of the 1996 tornado-related film Twister.

Definitions

A tornado is «a violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud».^[16] For a vortex to be classified as a tornado, it must be in contact with both the ground and the cloud base. Scientists have not yet created a complete definition of the word; for example, there is disagreement as to whether separate touchdowns of the same funnel constitute separate tornadoes.^[4] Tornado refers to the vortex of wind, not the condensation cloud.^[17][18]

Funnel cloud

A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds (as described by Bernoulli’s principle) and rapid rotation (due to cyclostrophic balance) usually causes water vapor in the air to become visible as a funnel cloud or condensation funnel.^[19]

There is some disagreement over the definition of funnel cloud and condensation funnel. According to the Glossary of Meteorology, a funnel cloud is any rotating cloud pendant from a cumulus or cumulonimbus, and thus most tornadoes are included under this definition.^[20] Among many meteorologists, the funnel cloud term is strictly defined as a rotating cloud which is not associated with strong winds at the surface, and condensation funnel is a broad term for any rotating cloud below a cumuliform cloud.^[4]

Tornadoes often begin as funnel clouds with no associated strong winds at the surface, although not all evolve into a tornado. However, many tornadoes are preceded by a funnel cloud. Most tornadoes produce strong winds at the surface while the visible funnel is still above the ground, so it is difficult to discern the difference between a funnel cloud and a tornado from a distance.^[4]

Outbreaks and families

Occasionally, a single storm will produce more than one tornado, either simultaneously or in succession. Multiple tornadoes produced by the same storm cell are referred to as a «tornado family».^[21] Several tornadoes are sometimes spawned from the same large-scale storm system. If there is no break in activity, this is considered a tornado outbreak, although there are various definitions. A period of several successive days with tornado outbreaks in the same general area (spawned by multiple weather systems) is a tornado outbreak sequence, occasionally called an extended tornado outbreak.^[16][22][23]

Characteristics

Size and shape

Most tornadoes take on the appearance of a narrow funnel, a few hundred yards (meters) across, with a small cloud of debris near the ground. Tornadoes may be obscured completely by rain or dust. These tornadoes are especially dangerous, as even experienced meteorologists might not see them.^[24] Tornadoes can appear in many shapes and sizes.

Small, relatively weak landspouts may be visible only as a small swirl of dust on the ground. Although the condensation funnel may not extend all the way to the ground, if associated surface winds are greater than 40 mph (64 km/h), the circulation is considered a tornado.^[17] A tornado with a nearly cylindrical profile and relative low height is sometimes referred to as a «stovepipe» tornado. Large single-vortex tornadoes can look like large wedges stuck into the ground, and so are known as «wedge tornadoes» or «wedges». The «stovepipe» classification is also used for this type of tornado, if it otherwise fits that profile. A wedge can be so wide that it appears to be a block of dark clouds, wider than the distance from the cloud base to the ground. Even experienced storm observers may not be able to tell the difference between a low-hanging cloud and a wedge tornado from a distance. Many, but not all major tornadoes are wedges.^[25]

Tornadoes in the dissipating stage can resemble narrow tubes or ropes, and often curl or twist into complex shapes. These tornadoes are said to be «roping out», or becoming a «rope tornado». When they rope out, the length of their funnel increases, which forces the winds within the funnel to weaken due to conservation of angular momentum.^[26] Multiple-vortex tornadoes can appear as a family of swirls circling a common center, or may be completely obscured by condensation, dust, and debris, appearing to be a single funnel.^[27]

In the United States, tornadoes are around 500 feet (150 m) across on average and stay on the ground for 5 miles (8.0 km).^[24] Yet, there is a wide range of tornado sizes. Weak tornadoes, or strong yet dissipating tornadoes, can be exceedingly narrow, sometimes only a few feet or couple meters across. One tornado was reported to have a damage path only 7 feet (2 m) long.^[24] On the other end of the spectrum, wedge tornadoes can have a damage path a mile (1.6 km) wide or more. A tornado that affected Hallam, Nebraska on May 22, 2004, was up to 2.5 miles (4.0 km) wide at the ground.^[3]

In terms of path length, the Tri-State Tornado, which affected parts of Missouri, Illinois, and Indiana on March 18, 1925, was on the ground continuously for 219 miles (352 km). Many tornadoes which appear to have path lengths of 100 miles (160 km) or longer are composed of a family of tornadoes which have formed in quick succession; however, there is no substantial evidence that this occurred in the case of the Tri-State Tornado.^[22] Modern reanalysis of the path suggests that the tornado may have begun 15 miles (24 km) further west than previously thought, lengthening its track.^[28]

Appearance

Tornadoes can have a wide range of colors, depending on the environment in which they form. Those which form in a dry environment can be nearly invisible, marked only by swirling debris at the base of the funnel. Condensation funnels which pick up little or no debris can be gray to white. While traveling over a body of water as a waterspout, they can turn very white or even blue. Funnels which move slowly, ingesting a lot of debris and dirt, are usually darker, taking on the color of debris. Tornadoes in the Great Plains can turn red because of the reddish tint of the soil, and tornadoes in mountainous areas can travel over snow-covered ground, turning white.^[24]

Lighting conditions are a major factor in the appearance of a tornado. A tornado which is «back-lit» (viewed with the sun behind it) appears very dark. The same tornado, viewed with the sun at the observer’s back, may appear gray or brilliant white. Tornadoes which occur near the time of sunset can be many different colors, appearing in hues of yellow, orange, and pink.^[14][30]

Dust kicked up by the winds of the parent thunderstorm, heavy rain and hail, and the darkness of night are all factors which can reduce the visibility of tornadoes. Tornadoes occurring in these conditions are especially dangerous, since only weather radar observations, or possibly the sound of an approaching tornado, serve as any warning to those in the storm’s path. Most significant tornadoes form under the storm’s updraft base, which is rain-free,^[31] making them visible.^[32] Also, most tornadoes occur in the late afternoon, when the bright sun can penetrate even the thickest clouds.^[22] Night-time tornadoes are often illuminated by frequent lightning.

There is mounting evidence, including Doppler On Wheels mobile radar images and eyewitness accounts, that most tornadoes have a clear, calm center with extremely low pressure, akin to the eye of tropical cyclones. This area would be clear (possibly full of dust), have relatively light winds, and be very dark, since the light would be blocked by swirling debris on the outside of the tornado. Lightning is said to be the source of illumination for those who claim to have seen the interior of a tornado.^[33][34][35]

Rotation

Tornadoes normally rotate cyclonically in direction (counterclockwise in the northern hemisphere, clockwise in the southern). While large-scale storms always rotate cyclonically due to the Coriolis effect, thunderstorms and tornadoes are so small that the direct influence of the Coriolis effect is unimportant, as indicated by their large Rossby numbers. Supercells and tornadoes rotate cyclonically in numerical simulations even when the Coriolis effect is neglected.^[36][37] Low-level mesocyclones and tornadoes owe their rotation to complex processes within the supercell and ambient environment.^[38]

Approximately 1 percent of tornadoes rotate in an anticyclonic direction in the northern hemisphere. Typically, systems as weak as landspouts and gustnadoes can rotate anticyclonically, and usually only those which form on the anticyclonic shear side of the descending rear flank downdraft in a cyclonic supercell.^[39] On rare occasions, anticyclonic tornadoes form in association with the mesoanticyclone of an anticyclonic supercell, in the same manner as the typical cyclonic tornado, or as a companion tornado either as a satellite tornado or associated with anticyclonic eddies within a supercell.^[40]

Sound and seismology

Tornadoes emit widely on the acoustics spectrum and the sounds are caused by multiple mechanisms. Various sounds of tornadoes have been reported throughout time, mostly related to familiar sounds for the witness and generally some variation of a whooshing roar. Popularly reported sounds include a freight train, rushing rapids or waterfall, a nearby jet engine, or combinations of these. Many tornadoes are not audible from much distance; the nature and propagation distance of the audible sound depends on atmospheric conditions and topography.

The winds of the tornado vortex and of constituent turbulent eddies, as well as airflow interaction with the surface and debris, contribute to the sounds. Funnel clouds also produce sounds. Funnel clouds and small tornadoes are reported as whistling, whining, humming, or the buzzing of innumerable bees or electricity, or more or less harmonic, whereas many tornadoes are reported as a continuous, deep rumbling, or an irregular sound of «noise».^[41]

Since many tornadoes are audible only when very near, sound is not reliable warning of a tornado. And, any strong, damaging wind, even a severe hail volley or continuous thunder in a thunderstorm may produce a roaring sound.^[42]

Tornadoes also produce identifiable inaudible infrasonic signatures.^[43]

Unlike audible signatures, tornadic signatures have been isolated; due to the long distance propagation of low-frequency sound, efforts are ongoing to develop tornado prediction and detection devices with additional value in understanding tornado morphology, dynamics, and creation.^[44] Tornadoes also produce a detectable seismic signature, and research continues on isolating it and understanding the process.^[45]

Electromagnetic, lightning, and other effects

Tornadoes emit on the electromagnetic spectrum, with sferics and E-field effects detected.^[44][46][47] There are observed correlations between tornadoes and patterns of lightning. Tornadic storms do not contain more lightning than other storms and some tornadic cells never produce lightning. More often than not, overall cloud-to-ground (CG) lightning activity decreases as a tornado reaches the surface and returns to the baseline level when the tornado lifts. In many cases, intense tornadoes and thunderstorms exhibit an increased and anomalous dominance of positive polarity CG discharges.^[48] Electromagnetics and lightning have little or nothing to do directly with what drives tornadoes (tornadoes are basically a thermodynamic phenomenon), although there are likely connections with the storm and environment affecting both phenomena.

Luminosity has been reported in the past and is probably due to misidentification of external light sources such as lightning, city lights, and power flashes from broken lines, as internal sources are now uncommonly reported and are not known to ever have been recorded. In addition to winds, tornadoes also exhibit changes in atmospheric variables such as temperature, moisture, and pressure. For example, on June 24, 2003 near Manchester, South Dakota, a probe measured a 100 mbar (hPa) (2.95 inHg) pressure decrease. The pressure dropped gradually as the vortex approached then dropped extremely rapidly to 850 mbar (hPa) (25.10 inHg) in the core of the violent tornado before rising rapidly as the vortex moved away, resulting in a V-shape pressure trace. Temperature tends to decrease and moisture content to increase in the immediate vicinity of a tornado.^[49]

Life cycle

Supercell relationship

Tornadoes often develop from a class of thunderstorms known as supercells. Supercells contain mesocyclones, an area of organized rotation a few miles up in the atmosphere, usually 1–6 miles (2–10 km) across. Most intense tornadoes (EF3 to EF5 on the Enhanced Fujita Scale) develop from supercells. In addition to tornadoes, very heavy rain, frequent lightning, strong wind gusts, and hail are common in such storms.

Most tornadoes from supercells follow a recognizable life cycle. That begins when increasing rainfall drags with it an area of quickly descending air known as the rear flank downdraft (RFD). This downdraft accelerates as it approaches the ground, and drags the supercell’s rotating mesocyclone towards the ground with it.^[17]

Formation

As the mesocyclone approaches the ground, a visible condensation funnel appears to descend from the base of the storm, often from a rotating wall cloud. As the funnel descends, the RFD also reaches the ground, creating a gust front that can cause damage a good distance from the tornado. Usually, the funnel cloud becomes a tornado within minutes of the RFD reaching the ground.^[17]

Maturity

Initially, the tornado has a good source of warm, moist inflow to power it, so it grows until it reaches the «mature stage». This can last anywhere from a few minutes to more than an hour, and during that time a tornado often causes the most damage, and in rare cases can be more than one mile (1.6 km) across. Meanwhile, the RFD, now an area of cool surface winds, begins to wrap around the tornado, cutting off the inflow of warm air which feeds the tornado.^[17]

Demise

As the RFD completely wraps around and chokes off the tornado’s air supply, the vortex begins to weaken, and become thin and rope-like. This is the «dissipating stage»; often lasting no more than a few minutes, after which the tornado fizzles. During this stage the shape of the tornado becomes highly influenced by the winds of the parent storm, and can be blown into fantastic patterns.^[22][29][30] Even though the tornado is dissipating, it is still capable of causing damage. The storm is contracting into a rope-like tube and, like the ice skater who pulls her arms in to spin faster, winds can increase at this point.^[26]

As the tornado enters the dissipating stage, its associated mesocyclone often weakens as well, as the rear flank downdraft cuts off the inflow powering it. In particular, intense supercells tornadoes can develop cyclically. As the first mesocyclone and associated tornado dissipate, the storm’s inflow may be concentrated into a new area closer to the center of the storm. If a new mesocyclone develops, the cycle may start again, producing one or more new tornadoes. Occasionally, the old (occluded) mesocyclone and the new mesocyclone produce a tornado at the same time.

Although this is a widely accepted theory for how most tornadoes form, live, and die, it does not explain the formation of smaller tornadoes, such as landspouts, long-lived tornadoes, or tornadoes with multiple vortices. These each have different mechanisms which influence their development—however, most tornadoes follow a pattern similar to this one.^[50]

Types

Multiple vortex

A multiple-vortex tornado is a type of tornado in which two or more columns of spinning air rotate around a common center. Multivortex structure can occur in almost any circulation, but is very often observed in intense tornadoes. These vortices often create small areas of heavier damage along the main tornado path.^[4][17] This is a distinct phenomenon from a satellite tornado, which is a weaker tornado which forms very near a large, strong tornado contained within the same mesocyclone. The satellite tornado may appear to «orbit» the larger tornado (hence the name), giving the appearance of one, large multi-vortex tornado. However, a satellite tornado is a distinct circulation, and is much smaller than the main funnel.^[4]

Waterspout

A waterspout is defined by the National Weather Service as a tornado over water. However, researchers typically distinguish «fair weather» waterspouts from tornadic waterspouts. Fair weather waterspouts are less severe but far more common, and are similar to dust devils and landspouts. They form at the bases of cumulus congestus clouds over tropical and subtropical waters. They have relatively weak winds, smooth laminar walls, and typically travel very slowly. They occur most commonly in the Florida Keys and in the northern Adriatic Sea.^[51][52][53] In contrast, tornadic waterspouts are stronger tornadoes over water. They form over water similarly to mesocyclonic tornadoes, or are stronger tornadoes which cross over water. Since they form from severe thunderstorms and can be far more intense, faster, and longer-lived than fair weather waterspouts, they are more dangerous.^[54]

Landspout

A landspout, or dust-tube tornado, is a tornado not associated with a mesocyclone. The name stems from their characterization as a «fair weather waterspout on land». Waterspouts and landspouts share many defining characteristics, including relative weakness, short lifespan, and a small, smooth condensation funnel which often does not reach the surface. Landspouts also create a distinctively laminar cloud of dust when they make contact with the ground, due to their differing mechanics from true mesoform tornadoes. Though usually weaker than classic tornadoes, they can produce strong winds which could cause serious damage.^[4][17]

Similar circulations

Gustnado

A gustnado, or gust front tornado, is a small, vertical swirl associated with a gust front or downburst. Because they are not connected with a cloud base, there is some debate as to whether or not gustnadoes are tornadoes. They are formed when fast moving cold, dry outflow air from a thunderstorm is blown through a mass of stationary, warm, moist air near the outflow boundary, resulting in a «rolling» effect (often exemplified through a roll cloud). If low level wind shear is strong enough, the rotation can be turned vertically or diagonally and make contact with the ground. The result is a gustnado.^[4][55] They usually cause small areas of heavier rotational wind damage among areas of straight-line wind damage.

Dust devil

A dust devil resembles a tornado in that it is a vertical swirling column of air. However, they form under clear skies and are no stronger than the weakest tornadoes. They form when a strong convective updraft is formed near the ground on a hot day. If there is enough low level wind shear, the column of hot, rising air can develop a small cyclonic motion that can be seen near the ground. They are not considered tornadoes because they form during fair weather and are not associated with any clouds. However, they can, on occasion, result in major damage in arid areas.^[24][56]

Fire whirls and steam devils

Small-scale, tornado-like circulations can occur near any intense surface heat source. Those that occur near intense wildfires are called fire whirls. They are not considered tornadoes, except in the rare case where they connect to a pyrocumulus or other cumuliform cloud above. Fire whirls usually are not as strong as tornadoes associated with thunderstorms. They can, however, produce significant damage.^[22] A steam devil is a rotating updraft that involves steam or smoke. Steam devils are very rare. They most often form from smoke issuing from a power plant smokestack. Hot springs and deserts may also be suitable locations for a steam devil to form. The phenomenon can occur over water, when cold arctic air passes over relatively warm water.^[24]

Intensity and damage

The Fujita scale and the Enhanced Fujita Scale rate tornadoes by damage caused. The Enhanced Fujita (EF) Scale was an upgrade to the older Fujita scale, by expert elicitation, using engineered wind estimates and better damage descriptions. The EF Scale was designed so that a tornado rated on the Fujita scale would receive the same numerical rating, and was implemented starting in the United States in 2007. An EF0 tornado will probably damage trees but not substantial structures, whereas an EF5 tornado can rip buildings off their foundations leaving them bare and even deform large skyscrapers. The similar TORRO scale ranges from a T0 for extremely weak tornadoes to T11 for the most powerful known tornadoes. Doppler weather radar data, photogrammetry, and ground swirl patterns (cycloidal marks) may also be analyzed to determine intensity and award a rating.^[4][57][58] Tornadoes vary in intensity regardless of shape, size, and location, though strong tornadoes are typically larger than weak tornadoes. The association with track length and duration also varies, although longer track tornadoes tend to be stronger.^[59] In the case of violent tornadoes, only a small portion of the path is of violent intensity, most of the higher intensity from subvortices.^[22]

In the United States, 80% of tornadoes are EF0 and EF1 (T0 through T3) tornadoes. The rate of occurrence drops off quickly with increasing strength—less than 1% are violent tornadoes (EF4, T8 or stronger).^[60] Outside Tornado Alley, and North America in general, violent tornadoes are extremely rare. This is apparently mostly due to the lesser number of tornadoes overall, as research shows that tornado intensity distributions are fairly similar worldwide. A few significant tornadoes occur annually in Europe, Asia, southern Africa, and southeastern South America, respectively.^[61]

Climatology

The United States has the most tornadoes of any country, nearly four times more than estimated in all of Europe, excluding waterspouts.^[62] This is mostly due to the unique geography of the continent. North America is a large continent that extends from the tropics north into arctic areas, and has no major east-west mountain range to block air flow between these two areas. In the middle latitudes, where most tornadoes of the world occur, the Rocky Mountains block moisture and buckle the atmospheric flow, forcing drier air at mid-levels of the troposphere due to downsloped winds, and causing the formation of a low pressure area downwind to the east of the mountains. Increased westerly flow off the Rockies force the formation of a dry line when the flow aloft is strong,^[63] while the Gulf of Mexico fuels abundant low-level moisture in the southerly flow to its east. This unique topography allows for frequent collisions of warm and cold air, the conditions that breed strong, long-lived storms throughout the year. A large portion of these tornadoes form in an area of the central United States known as Tornado Alley.^[7] This area extends into Canada, particularly Ontario and the Prairie Provinces, although southeast Quebec, the interior of British Columbia, and western New Brunswick are also tornado-prone.^[64] Tornadoes also occur across northeastern Mexico.^[4]

The United States averages about 1,200 tornadoes per year. The Netherlands has the highest average number of recorded tornadoes per area of any country (more than 20, or 0.0013 per sq mi (0.00048 per km²), annually), followed by the UK (around 33, or 0.00035 per sq mi (0.00013 per km²), per year),^[65][66] but most are small and cause minor damage. In absolute number of events, ignoring area, the UK experiences more tornadoes than any other European country, excluding waterspouts.^[62]

Tornadoes kill an average of 179 people per year in Bangladesh, the most in the world. This is due to high population density, poor quality of construction and lack of tornado safety knowledge, as well as other factors.^[67][68] Other areas of the world that have frequent tornadoes include South Africa, parts of Argentina, Paraguay, and southern Brazil, as well as portions of Europe, Australia and New Zealand, and far eastern Asia.^[9][69]

Tornadoes are most common in spring and least common in winter.^[22] Spring and fall experience peaks of activity as those are the seasons when stronger winds, wind shear, and atmospheric instability are present.^[70] Tornadoes are focused in the right front quadrant of landfalling tropical cyclones, which tend to occur in the late summer and autumn. Tornadoes can also be spawned as a result of eyewall mesovortices, which persist until landfall.^[71] Favorable conditions can occur any time of the year.

Tornado occurrence is highly dependent on the time of day, because of solar heating.^[72] Worldwide, most tornadoes occur in the late afternoon, between 3 pm and 7 pm local time, with a peak near 5 pm.^{[73][74][75][76][77]} Destructive tornadoes can occur at any time of day. The Gainesville Tornado of 1936, one of the deadliest tornadoes in history, occurred at 8:30 am local time.^[22]

Associations with climate and climate change

Associations to various climate and environmental trends exist. For example, an increase in the sea surface temperature of a source region (e.g. Gulf of Mexico and Mediterranean Sea) increases atmospheric moisture content. Increased moisture can fuel an increase in severe weather and tornado activity, particularly in the cool season.^[78]

Some evidence does suggest that the Southern Oscillation is weakly correlated with changes in tornado activity, which vary by season and region, as well as whether the ENSO phase is that of El Niño or La Niña.^[79]

Climatic shifts may affect tornadoes via teleconnections in shifting the jet stream and the larger weather patterns. The climate-tornado link is confounded by the forces affecting larger patterns and by the local, nuanced nature of tornadoes. Although it is reasonable that global warming may affect trends in tornado activity,^[80] any such effect is not yet identifiable due to the complexity, local nature of the storms, and database quality issues. Any effect would vary by region.^[81]

Detection

Rigorous attempts to warn of tornadoes began in the United States in the mid-20th century. Before the 1950s, the only method of detecting a tornado was by someone seeing it on the ground. Often, news of a tornado would reach a local weather office after the storm. However, with the advent of weather radar, areas near a local office could get advance warning of severe weather. The first public tornado warnings were issued in 1950 and the first tornado watches and convective outlooks in 1952. In 1953 it was confirmed that hook echoes are associated with tornadoes.^[82] By recognizing these radar signatures, meteorologists could detect thunderstorms probably producing tornadoes from dozens of miles away.^[83]

Radar

Today, most developed countries have a network of weather radars, which remains the main method of detecting signatures probably associated with tornadoes. In the United States and a few other countries, Doppler weather radar stations are used. These devices measure the velocity and radial direction (towards or away from the radar) of the winds in a storm, and so can spot evidence of rotation in storms from more than a hundred miles (160 km) away. When storms are distant from a radar, only areas high within the storm are observed and the important areas below are not sampled.^[84] Data resolution also decreases with distance from the radar. Some meteorological situations leading to tornadogenesis are not readily detectable by radar and on occasion tornado development may occur more quickly than radar can complete a scan and send the batch of data. Also, most populated areas on Earth are now visible from the Geostationary Operational Environmental Satellites (GOES), which aid in the nowcasting of tornadic storms.^[85]

Storm spotting

In the mid-1970s, the U.S. National Weather Service (NWS) increased its efforts to train storm spotters to spot key features of storms which indicate severe hail, damaging winds, and tornadoes, as well as damage itself and flash flooding. The program was called Skywarn, and the spotters were local sheriff’s deputies, state troopers, firefighters, ambulance drivers, amateur radio operators, civil defense (now emergency management) spotters, storm chasers, and ordinary citizens. When severe weather is anticipated, local weather service offices request that these spotters look out for severe weather, and report any tornadoes immediately, so that the office can warn of the hazard.

Usually spotters are trained by the NWS on behalf of their respective organizations, and report to them. The organizations activate public warning systems such as sirens and the Emergency Alert System, and forward the report to the NWS.^[86] There are more than 230,000 trained Skywarn weather spotters across the United States.^[87]

In Canada, a similar network of volunteer weather watchers, called Canwarn, helps spot severe weather, with more than 1,000 volunteers.^[85] In Europe, several nations are organizing spotter networks under the auspices of Skywarn Europe^[88] and the Tornado and Storm Research Organisation (TORRO) has maintained a network of spotters in the United Kingdom since 1974.^[89]

Storm spotters are needed because radar systems such as NEXRAD do not detect a tornado; merely signatures which hint at the presence of tornadoes.^[90] Radar may give a warning before there is any visual evidence of a tornado or imminent tornado, but ground truth from an observer can either verify the threat or determine that a tornado is not imminent.^[91] The spotter’s ability to see what radar cannot is especially important as distance from the radar site increases, because the radar beam becomes progressively higher in altitude further away from the radar, chiefly due to curvature of Earth, and the beam also spreads out.^[84]

Visual evidence

Storm spotters are trained to discern whether a storm seen from a distance is a supercell. They typically look to its rear, the main region of updraft and inflow. Under the updraft is a rain-free base, and the next step of tornadogenesis is the formation of a rotating wall cloud. The vast majority of intense tornadoes occur with a wall cloud on the backside of a supercell.^[60]

Evidence of a supercell comes from the storm’s shape and structure, and cloud tower features such as a hard and vigorous updraft tower, a persistent, large overshooting top, a hard anvil (especially when backsheared against strong upper level winds), and a corkscrew look or striations. Under the storm and closer to where most tornadoes are found, evidence of a supercell and likelihood of a tornado includes inflow bands (particularly when curved) such as a «beaver tail», and other clues such as strength of inflow, warmth and moistness of inflow air, how outflow- or inflow-dominant a storm appears, and how far is the front flank precipitation core from the wall cloud. Tornadogenesis is most likely at the interface of the updraft and rear flank downdraft, and requires a balance between the outflow and inflow.^[17]

Only wall clouds that rotate spawn tornadoes, and usually precede the tornado by five to thirty minutes. Rotating wall clouds are the visual manifestation of a mesocyclone. Barring a low-level boundary, tornadogenesis is highly unlikely unless a rear flank downdraft occurs, which is usually visibly evidenced by evaporation of cloud adjacent to a corner of a wall cloud. A tornado often occurs as this happens or shortly after; first, a funnel cloud dips and in nearly all cases by the time it reaches halfway down, a surface swirl has already developed, signifying a tornado is on the ground before condensation connects the surface circulation to the storm. Tornadoes may also occur without wall clouds, under flanking lines, and on the leading edge. Spotters watch all areas of a storm, and the cloud base and surface.^[92]

Extremes

The most extreme tornado in recorded history was the Tri-State Tornado, which roared through parts of Missouri, Illinois, and Indiana on March 18, 1925. It was likely an F5, though tornadoes were not ranked on any scale in that era. It holds records for longest path length (219 miles, 352 km), longest duration (about 3.5 hours), and fastest forward speed for a significant tornado (73 mph, 117 km/h) anywhere on Earth. In addition, it is the deadliest single tornado in United States history (695 dead).^[22] The tornado was also the second costliest tornado in history at the time, but in the years since has been surpassed by several others if population changes over time are not considered. When costs are normalized for wealth and inflation, it ranks third today.^[93]

The deadliest tornado in world history was the Daultipur-Salturia Tornado in Bangladesh on April 26, 1989, which killed approximately 1300 people.^[67] Bangladesh has had at least 19 tornadoes in its history kill more than 100 people, almost half of the total in the rest of the world.

The most extensive tornado outbreak on record was the Super Outbreak, which affected a large area of the central United States and extreme southern Ontario in Canada on April 3 and 4, 1974. This outbreak, which saw 148 tornadoes develop in 18 hours, included six of F5 intensity and twenty-four that peaked at F4 strength. Sixteen tornadoes were on the ground at the same time during its peak. More than 300 people, possibly as many as 330, were killed by tornadoes during this outbreak.^[94]

While direct measurement of the most violent tornado wind speeds is nearly impossible, since conventional anemometers would be destroyed by the intense winds, some tornadoes have been scanned by mobile Doppler radar units, which can provide a good estimate of the tornado’s winds. The highest wind speed ever measured in a tornado, which is also the highest wind speed ever recorded on the planet, is 301 ± 20 mph (484 ± 32 km/h) in the F5 Bridge Creek-Moore, Oklahoma, tornado which killed 36 people.^[95] Though the reading was taken about 100 feet (30 m) above the ground, this is a testament to the power of the strongest tornadoes.^[2]

Storms that produce tornadoes can feature intense updrafts, sometimes exceeding 150 mph (240 km/h). Debris from a tornado can be lofted into the parent storm and carried a very long distance. A tornado which affected Great Bend, Kansas, in November 1915, was an extreme case, where a «rain of debris» occurred 80 miles (130 km) from the town, a sack of flour was found 110 miles (180 km) away, and a cancelled check from the Great Bend bank was found in a field outside of Palmyra, Nebraska, 305 miles (491 km) to the northeast.^[96] Waterspouts and tornadoes have been advanced as an explanation for instances of raining fish and other animals.^[97]

Safety

Though tornadoes can strike in an instant, there are precautions and preventative measures that people can take to increase the chances of surviving a tornado. Authorities such as the Storm Prediction Center advise having a pre-determined plan should a tornado warning be issued. When a warning is issued, going to a basement or an interior first-floor room of a sturdy building greatly increases chances of survival.^[98] In tornado-prone areas, many buildings have storm cellars on the property. These underground refuges have saved thousands of lives.^[99]

Some countries have meteorological agencies which distribute tornado forecasts and increase levels of alert of a possible tornado (such as tornado watches and warnings in the United States and Canada). Weather radios provide an alarm when a severe weather advisory is issued for the local area, though these are mainly available only in the United States. Unless the tornado is far away and highly visible, meteorologists advise that drivers park their vehicles far to the side of the road (so as not to block emergency traffic), and find a sturdy shelter. If no sturdy shelter is nearby, getting low in a ditch is the next best option. Highway overpasses are one of the worst places to take shelter during tornadoes, as they are believed to create a Venturi effect, increasing the danger from the tornado by increasing the wind speed and funneling debris underneath the overpass.^[100]

Myths and misconceptions

Folklore often identifies a green sky with tornadoes, and though the phenomenon may be associated with severe weather, there is no evidence linking it specifically with tornadoes.^[101] It is often thought that opening windows will lessen the damage caused by the tornado. While there is a large drop in atmospheric pressure inside a strong tornado, it is unlikely that the pressure drop would be enough to cause the house to explode. Some research indicates that opening windows may actually increase the severity of the tornado’s damage. A violent tornado can destroy a house whether its windows are open or closed.^[102][103]

Another commonly held belief is that highway overpasses provide adequate shelter from tornadoes. On the contrary, a highway overpass is a dangerous place during a tornado. In the 1999 Oklahoma tornado outbreak of May 3, 1999, three highway overpasses were directly struck by tornadoes, and at all three locations there was a fatality, along with many life-threatening injuries. The small area under the overpasses is believed to cause a Venturi effect.^[104] By comparison, during the same tornado outbreak, more than 2000 homes were completely destroyed, with another 7000 damaged, and yet only a few dozen people died in their homes.^[100]

An old belief is that the southwest corner of a basement provides the most protection during a tornado. The safest place is the side or corner of an underground room opposite the tornado’s direction of approach (usually the northeast corner), or the central-most room on the lowest floor. Taking shelter in a basement, under a staircase, or under a sturdy piece of furniture such as a workbench further increases chances of survival.^[102][103]

Finally, there are areas which people believe to be protected from tornadoes, whether by being in a city, near a major river, hill, or mountain, or even protected by supernatural forces.^[105] Tornadoes have been known to cross major rivers, climb mountains,^[106] affect valleys, and have damaged several city centers. As a general rule, no area is «safe» from tornadoes, though some areas are more susceptible than others.^{[24][102][103]}

One long-held myth was that no city whose name begins with the letter X would ever be hit by a tornado, the letter X as an initial letter of a place-name in the United States being extremely rare—until Xenia, Ohio experienced an F-5 tornado that killed 34 people in 1974.

Ongoing research

Meteorology is a relatively young science and the study of tornadoes is newer still. Although researched for about 140 years and intensively for around 60 years, there are still aspects of tornadoes which remain a mystery.^[107] Scientists have a fairly good understanding of the development of thunderstorms and mesocyclones,^[108][109] and the meteorological conditions conducive to their formation. However, the step from supercell (or other respective formative processes) to tornadogenesis and predicting tornadic vs. non-tornadic mesocyclones is not yet well known and is the focus of much research.^[70]

Also under study are the low-level mesocyclone and the stretching of low-level vorticity which tightens into a tornado,^[70] namely, what are the processes and what is the relationship of the environment and the convective storm. Intense tornadoes have been observed forming simultaneously with a mesocyclone aloft (rather than succeeding mesocyclogenesis) and some intense tornadoes have occurred without a mid-level mesocyclone. In particular, the role of downdrafts, particularly the rear-flank downdraft, and the role of baroclinic boundaries, are intense areas of study.^[110]

Reliably predicting tornado intensity and longevity remains a problem, as do details affecting characteristics of a tornado during its life cycle and tornadolysis. Other rich areas of research are tornadoes associated with mesovortices within linear thunderstorm structures and within tropical cyclones.^[111]

Scientists still do not know the exact mechanisms by which most tornadoes form, and occasional tornadoes still strike without a tornado warning being issued.^[112] Analysis of observations including both stationary and mobile (surface and aerial) in-situ and remote sensing (passive and active) instruments generates new ideas and refines existing notions. Numerical modeling also provides new insights as observations and new discoveries are integrated into our physical understanding and then tested in computer simulations which validate new notions as well as produce entirely new theoretical findings, many of which are otherwise unattainable. Importantly, development of new observation technologies and installation of finer spatial and temporal resolution observation networks have aided increased understanding and better predictions.^[113]

Research programs, including field projects such as the VORTEX projects (Verification of the Origins of Rotation in Tornadoes Experiment), deployment of TOTO (the TOtable Tornado Observatory), Doppler On Wheels (DOW), and dozens of other programs, hope to solve many questions that still plague meteorologists.^[44] Universities, government agencies such as the National Severe Storms Laboratory, private-sector meteorologists, and the National Center for Atmospheric Research are some of the organizations very active in research; with various sources of funding, both private and public, a chief entity being the National Science Foundation.^[90][114]

See also

• Cultural significance of tornadoes
• Derecho
• History of tropical cyclone-spawned tornadoes
• List of tornadoes and tornado outbreaks
• Secondary flow
• Skipping tornado
• Tornado drill
• Tornadoes of 2011
• Whirlwind (atmospheric phenomenon)

References

Further reading

• Howard B Bluestein (1999). Tornado Alley: Monster Storms of the Great Plains. New York, NY: Oxford University Press. ISBN 0-19-510552-4.
• Marlene Bradford (2001). Scanning the Skies: a History of Tornado Forecasting. University of Oklahoma Press. ISBN 0-8061-3302-3.
• Thomas P Grazulis (January 1997). Significant Tornadoes Update, 1992–1995. St. Johnsbury, VT: Environmental Films. ISBN 1-879362-04-X.

External links

• NOAA Storm Database 1950–Present
• European Severe Weather Database
• Social & Economic Costs of Tornadoes
• Tornado Detection and Warnings
• Electronic Journal of Severe Storms Meteorology
• NOAA Tornado Preparedness Guide
• Tornado History Project — Maps and statistics from 1950-Present

1	0   0 A vortex of rapidly moving air associated with some severe thunderstorms. Winds within the tornado funnel may exceed 500 kilometers per hour.

2	0   0 Tornado A violently rotating column of air, usually pendant to a cumulonimbus, with circulation reaching the ground. It nearly always starts as a funnel cloud and may be accompanied by a loud roaring noise. O [..]

3	0   0 Tornado 1550s, ternado, navigator’s word for violent windy thunderstorm in the tropical Atlantic, probably a mangled borrowing from Spanish tronada «thunderstorm,» from tronar «to thunder, [..]

4	0   0 Tornado An intense, rotating column of air that protrudes from a cumulonimbus cloud in the shape of a funnel or a rope and touches the ground. (See Funnel cloud.)

5	0   0 Tornado a violently rotating column of air that forms at the bottom of a cloud and touches the ground.

6	0   0 Tornado A rotating column of air, in contact with the surface, pendant from a cumuliform cloud, and often visible as a funnel cloud and/or circulating debris/dust at the ground. On a local scale, the tornado [..]

7	0   0 Tornado A whirlwind or mass of rotating air with high wind speeds at its center.

8	0   0 Tornado a localized and violently destructive windstorm occurring over land characterized by a funnel-shaped cloud extending toward the ground crack: a purified and potent form of cocaine that is smoked rathe [..]

9	0   0 Tornado a localized, anti-clockwise spiral of wind with extremely violent wind speed and uplift.

10	0   0 Tornado A violent rotating column of air, in contact with the ground, pendant from a cumulonimbus cloud. A tornado does not require the visible presence of a funnel cloud. It has a typical width of tens to hu [..]

11	0   0 Tornado A small but extremely violent storm. The distinctive funnel clouds descend to the ground from the base of a thundercloud and can be up to 100 metres at the base.

12	0   0 Tornado If you dream that you are in a tornado, you will be filled with disappointment and perplexity over the miscarriage of studied plans for swift attainment of fortune. See Hurricane.

13	0   0 Tornado (n) — a narrow, cyclonic storm with very high wind speeds

14	0   0 Tornado A destructive windstorm occurring over land, characterized by a funnel-shaped cloud extending toward the ground.

15	0   0 Tornado A destructive, whirling, funnel-shaped cloud that has extremely low air pressure.

16	0   0 Tornado A violent storm characterized by a funnel-shaped cloud and high winds.

17	0   0 Tornado destructive, rotating column of air that has very high wind speeds and that may be visible as a funnel-shaped cloud. total eclipse —

18	0   0 Tornado A rotating column of air usually accompanied by a funnel-shaped downward extension of a cumulonimbus cloud and having a vortex several hundred yards in diameter whirling destructively at speeds of up to 500 miles (800 kilometers) per hour.

19	0   0 Tornado (n) a localized and violently destructive windstorm occurring over land characterized by a funnel-shaped cloud extending toward the ground(n) a purified and potent form of cocaine that is smoked rat [..]

20	0   0 Tornado Concentrated storms that are characterized by a funnel-shaped cloud and extreme winds (Lesson 28)

21	0   0 Tornado A violent rotating column of air, extending from the base of a cumulonimbus cloud to the ground, producing damaging winds up to 300 mph. TROPICAL DEPRESSION: A tropical cyclone in which the maximum 1- [..]

22	0   0 Tornado A violent rotating column of air, in contact with the ground, pendant from a cumulonimbus cloud. A tornado does not require the visible presence of a funnel cloud. It has a typical width of tens to hu [..]

23	0   0 Tornado A violently rotating column of air in contact with and extending between a convective cloud and the surface of the earth. It is the most destructive of all storm-scale atmospheric phenomena. They can [..]

24	0   0 Tornado Rotating column of air extending from a thunderstorm to the ground. Tornadoes generally produce damage paths of 100 yards wide or less, with path lengths of a couple miles.

25	0   0 Tornado A violently rotating column of air that reaches from the base of a cloud to the ground.

26	0   0 Tornado Whirlwind having a diameter of less than a quarter of a mile, and a speed of travel of about 30 knots. Wind velocity may exceed 200 knots. Local effects may be disastrous.

27	0   0 Tornado A whirling wind over land, accompanied by a funnel-shaped cloud. It is usually very violent and destructive in a narrow path, often for many miles.

28	0   0 Tornado A twisting, spinning funnel of low pressure air. The most unpredictable weather event, tornadoes are created during powerful thunderstorms. As a column of warm air rises, air rushes in at ground level [..]

29	0   0 Tornado A rotating column of air usually accompanied by a funnel-shaped downward extension of a cumulonimbus cloud and having a vortex several hundred yards in diameter whirling destructively at speeds of up to 500 miles (800 kilometers) per hour.

30

0   0 Tornado A violently rotating column of air in contact with the ground and extending from the base of a thunderstorm. A condensation funnel does not need to reach to the ground for a tornado to be present; a debris cloud beneath a thunderstorm is all that is needed to confirm the presence of a tornado, even in the total absence of a condensation funnel. It [..]

31	0   0 Tornado Rapidly spinning wind shaped like a cone or funnel. Conditions are ripe for tornadoes when the air becomes unstable inside a big thunderstorm, with blowing winds creating rolling air currents. When it [..]

32	0   0 Tornado A violently rotating column of air, usually pendant to a cumulonimbus, with circulation reaching the ground. It nearly always starts as a funnel cloud and may be accompanied by a loud roaring noise. On a local scale, it is the most destructive of all atmospheric phenomena.

33

0   0 Tornado A rotating column of air that stretches from the base of a cumulonimbus or towering cumulus cloud. This is the most intense atmospheric phenomena and takes the shape of a funnel cloud. A tornado develops from a funnel cloud with strong and violent rotation that extends entirely to the surface. Upon impact with the ground, strong winds associated wi [..]

34	0   0 Tornado A rapidly rotating column of air extending from a cumulonimbus cloud with a circulation that reaches the ground. However, the visible portion might not extend all the way to the ground. Tornado Warnin [..]

35

0   0 Tornado A violently rotating column of air in contact with the ground and extending from the base of a thunderstorm. A condensation funnel does not need to reach to the ground for a tornado to be present; a debris cloud beneath a thunderstorm is all that is needed to confirm the presence of a tornado, even in the total absence of a condensation funnel.

36	0   0 Tornado An intense, rotating column of air that protrudes from a cumulonimbus cloud in the shape of a funnel or a rope whose circulation is present on the ground.

37	0   0 Tornado A rotating column of air, usually accompanied by a funnel shaped downward extension of a cumulonimbus cloud, perhaps several hundred yards or more in diameter, whirling destructively at speeds sometimes in excess of 300 miles per hour. Also called a twister.

38	0   0 Tornado A violently rotating column of air in contact with the ground. It typically forms from a thunderstorm. Tornadoes are ranked F0 to F5 on the Fujita Tornado Intensity Scale based on their intensity and [..]

39	0   0 Tornado A rapidly rotating column of air extending from a cumulonimbus cloud with a circulation that reaches the ground.

40	0   0 Tornado A violently rotating column of air, in contact with the surface, pendant from a cumuliform cloud, and often (but not always) visible as a funnel cloud. Wind speeds are sometimes estimated on the basis [..]

41

0   0 Tornado A violently rotating column of air in contact with and extending between a convective cloud and the surface of the earth. It is the most destructive of all storm-scale atmospheric phenomena. They can occur anywhere in the world given the right conditions, but are most frequent in the United States in an area bounded by the Rockies on the west and t [..]

42	0   0 Tornado A violently rotating column of air, usually pendant to a cumulonimbus, with circulation reaching the ground. It nearly always starts as a funnel cloud and may be accompanied by a loud roaring noise. O [..]

43	0   0 Tornado A small mass of air that whirls rapidly about an almost vertical axis; made visible by clouds and by dust and debris sucked into the system.

44

0   0 Tornado A violent rotating column of air, usually forming a pendant from a cumulonimbus cloud with the circulation reaching the ground. It nearly always starts as a funnel cloud and may be accompanied by a loud roaring noise. On a local scale, it is the most destructive of all atmospheric phenomena.

45	0   0 Tornado A violently rotating column of air in contact with and extending between a convective cloud and the surface of the earth. It is the most destructive of all storm-scale atmospheric phenomena. They can [..]

46	0   0 Tornado A violently rotating column of air that is in contact with the ground. Sometimes a condensation funnel is not obvious for the entire length, cloud to ground, but even so, a debris cloud will be visibl [..]

47	0   0 Tornado A violently rotating column of air in contact with the ground and extending from the base of a thunderstorm. A condensation funnel does not need to reach to the ground for a tornado to be present; a d [..]

48	0   0 Tornado A violently rotating column of air in contact with and extending between a convective cloud and the surface of the earth. It is the most destructive of all storm-scale atmospheric phenomena. They can [..]

49	0   0 Tornado A violent, funnel-shaped rotating column of air that has contact with the earth’s surface and is extended from a thunderstorm base.

50	0   0 Tornado A violently rotating column of air in contact with and extending between a convective cloud and the surface of the earth. It is the most destructive of all storm-scale

51

0   0 Tornado Tornadoes are rapidly rotating columns of air that blow around a small area of intense low pressure. A Tornado in circulation is present on the ground either as a funnel shaped cloud or a swirling cloud of dust and debris. Some Tornadoes never reach the ground, and they appear to hang from a parent cloud as a rapidly rotating funnel. Most tornadoes [..]

52	0   0 Tornado A violently rotating column of air, usually pendant to a cumulonimbus, with circulation reaching the ground. It nearly always starts as a funnel cloud and may be accompanied by a loud roaring noise. O [..]

53	0   0 Tornado A strong, rotating column of air extending from the base of a cumulonimbus cloud to

54

0   0 Tornado A violently rotating column of air in contact with and extending between a convective cloud and the surface of the earth. It is the most destructive of all storm-scale atmospheric phenomena. They can occur anywhere in the world given the right conditions, but are most frequent in the United States in an area bounded by the Rockies on the west and t [..]

55	0   0 Tornado The Tornado is a double handed multihull class recognised as an International Class by the International Sailing Federation. It was used for the Catamaran discipline at the Olympic Games from 1976 to [..]

56	0   0 Tornado A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to a [..]

57	0   0 Tornado The Tornado is a double handed multihull class recognised as an International Class by the International Sailing Federation. It was used for the Catamaran discipline at the Olympic Games from 1976 to [..]

58	0   0 Tornado A tornado is a violent rotating column of air that touches the surface of the earth. Tornado may also refer to:

59	0   0 Tornado A tornado is a violent rotating column of air that touches the surface of the earth. Tornado may also refer to:

60	0   0 Tornado Tornado was a short-lived weekly British comic magazine published for 22 issues by IPC Magazines between March 1979 and August 1979. After the cancellations of the Starlord and Action titles, IPC laun [..]

61	0   0 Tornado Tornado was a short-lived weekly British comic magazine published for 22 issues by IPC Magazines between March 1979 and August 1979. After the cancellations of the Starlord and Action titles, IPC laun [..]

62	0   0 Tornado Tornado was a competitor on the UK TV series Robot Wars, noteworthy as the champion of the sixth series. It was built by Andrew Marchant, Bryan Moss and David Gamble, from Sawtry, near Huntingdon.

63	0   0 Tornado Tornado was a competitor on the UK TV series Robot Wars, noteworthy as the champion of the sixth series. It was built by Andrew Marchant, Bryan Moss and David Gamble, from Sawtry, near Huntingdon.

64	0   0 Tornado Tornado (occasionally Toronado) is a horse ridden by the character Zorro in several films and books. Tornado is said to be intelligent and fast. His name is pronounced in the Spanish way, «tor-NAH-do» [..]

65	0   0 Tornado The Tornado is a wooden roller coaster located at Adventureland in Altoona, Iowa, near Des Moines. The Tornado made its debut on July 4, 1978, during Adventureland’s third full season. It was designed [..]

66	0   0 Tornado A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to a [..]

67	0   0 Tornado A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to a [..]

68	0   0 Tornado Tornado is a 1943 film directed by William A. Berke and starring Chester Morris and Nancy Kelly.

69	0   0 Tornado Tornado is a combat flight simulator video game by Digital Integration that models the Panavia Tornado. It was released in 1993 for DOS and Amiga. Tornado is one of the first flight simulations to off [..]

70	0   0 Tornado Steve Debbes (born April 3, 1966), better known by his ring name Tornado, is a South African professional wrestler performing for World Wrestling Professionals. He is a 2-time WWP Heavyweight World Ch [..]

71	0   0 Tornado Tornado (1996) is a children’s book by Betsy Byars, illustrated by Doron Ben-Ami.

72	0   0 Tornado The Tornado is an amusement ride manufactured by Wisdom Industries Ltd. Most Tornadoes travel with a traveling midway company to many fairs with many other rides.

73	0   0 Tornado Tornado is a video game for the Nintendo DS handheld gaming system, developed by South Korean studio SKONEC Entertainment and published by Ignition Entertainment. The game tasks you as Toki, a member [..]

74	0   0 Tornado Tornado is brand of table football (foosball) table that has been used in the World Championships since 1986. The original Tornado model was created by engineer Bob Furr. The Tornado brand has been m [..]

75	0   0 Tornado Tornado (formerly known as Bobs) was a roller coaster located at Coney Island along Bowery Street in Brooklyn, New York City. Designed by Fred Church and built by the L. A. Thompson Company, the roll [..]

76	0   0 Tornado Tornado is a scalable, non-blocking web server and web application framework written in Python. It was developed for use by FriendFeed; the company was acquired by Facebook in 2009 and Tornado was ope [..]

77	0   0 Tornado A tornado is a violent rotating column of air that touches the surface of the earth. Tornado may also refer to:

78	0   0 Tornado The Tornado is a water slide manufactured by ProSlide Technology. It requires riders to sit in a 2-6 seater round tube. Riders drop from inside a tunnel out into the ride’s main element shaped like a [..]

79	0   0 Tornado «Tornado» is a song recorded by American country music group Little Big Town. It was released in October 2012 as the second single from their fifth studio album, Tornado. The song was written by Nata [..]

80	0   0 Tornado The Tornado is a steel inverted roller coaster at the Parque de Atracciones de Madrid in Casa de Campo, Madrid, Spain. Manufactured by Intamin, it opened on May 23, 1999.

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Today, the technology is there to give early and normally ample warning when a powerful tornado approaches. When a tornado strikes, all of us are at risk.

Spencer Bachus

ETYMOLOGY OF THE WORD TORNADO

Probably alteration of Spanish tronada thunderstorm (from tronar to thunder, from Latin tonāre), through influence of tornar to turn, from Latin tornāre to turn in a lathe.

PRONUNCIATION OF TORNADO

GRAMMATICAL CATEGORY OF TORNADO

Tornado is a noun.

WHAT DOES TORNADO MEAN IN ENGLISH?

Definition of tornado in the English dictionary

The first definition of tornado in the dictionary is Also called: cyclone, twister. a violent storm with winds whirling around a small area of extremely low pressure, usually characterized by a dark funnel-shaped cloud causing damage along its path. Other definition of tornado is a small but violent squall or whirlwind, such as those occurring on the West African coast. Tornado is also any violently active or destructive person or thing.

WORDS THAT RHYME WITH TORNADO

SYNONYMS OF «TORNADO»

The following words have a similar or identical meaning as «tornado» and belong to the same grammatical category.

TRANSLATION OF TORNADO

Find out the translation of tornado to 25 languages with our English multilingual translator.

TENDENCIES OF USE OF THE TERM «TORNADO»

The term «tornado» is very widely used and occupies the 9.404 position in our list of most widely used terms in the English dictionary.

Principal search tendencies and common uses of tornado

FREQUENCY OF USE OF THE TERM «TORNADO» OVER TIME

10 QUOTES WITH «TORNADO»

Famous quotes and sentences with the word tornado.

10 ENGLISH BOOKS RELATING TO «TORNADO»

Discover the use of tornado in the following bibliographical selection. Books relating to tornado and brief extracts from same to provide context of its use in English literature.

10 NEWS ITEMS WHICH INCLUDE THE TERM «TORNADO»

Find out what the national and international press are talking about and how the term tornado is used in the context of the following news items.

REFERENCE

« EDUCALINGO. Tornado [online]. Available <https://educalingo.com/en/dic-en/tornado>. Apr 2023 ».

tor·na·do

 (tôr-nā′dō)

n. pl. tor·na·does or tor·na·dos

1. A violently rotating column of air extending from a cumulonimbus cloud to the ground, ranging in width from a few meters to more than a kilometer, with destructive winds up to 510 kilometers (316 miles) per hour or higher. Tornadoes are typically associated with a funnel cloud pendant from a storm’s wall cloud, often extending to the bottom of the tornado.

2. A violent thunderstorm in western Africa or nearby Atlantic waters.

3. A whirlwind or hurricane.

---

[Alteration (probably influenced by Spanish tornado, turned, past participle of tornar, to turn) of Early Modern English ternado, violent thunderstorm, hurricane from Spanish tronada, thunderstorm, from tronar, to thunder, from Latin tonāre; see (s)tenə- in Indo-European roots.]

---

tor·na′dic (-nā′dĭk, -năd′ĭk) adj.

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

tornado

(tɔːˈneɪdəʊ)

n, pl -does or -dos

1. (Physical Geography) Also called: cyclone or twister (US and Canadian informal)a violent storm with winds whirling around a small area of extremely low pressure, usually characterized by a dark funnel-shaped cloud causing damage along its path

2. (Physical Geography) a small but violent squall or whirlwind, such as those occurring on the West African coast

3. any violently active or destructive person or thing

4. (often capital) a type of dinghy, designed to be crewed by two people

[C16: probably alteration of Spanish tronada thunderstorm (from tronar to thunder, from Latin tonāre), through influence of tornar to turn, from Latin tornāre to turn in a lathe]

tornadic adj

torˈnado-ˌlike adj

Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

tor•na•do

(tɔrˈneɪ doʊ)

n., pl. -does, -dos.

1. a localized, violently destructive windstorm occurring over land, esp. in the Middle West, and characterized by a long, funnel-shaped cloud that extends to the ground.

2. a violent squall or whirlwind of small extent, as one of those occurring during the summer on the W coast of Africa.

3. a violent outburst, as of emotion or activity.

[1550–60; appar. by metathesis < Sp tronada thunderstorm, n. use of feminine of tronado, past participle of tronar < Latin tonāre to thunder]

tor•nad′ic (-ˈnæd ɪk, -ˈneɪ dɪk) adj.

Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.

tor·na·do

(tôr-nā′dō)

A violently rotating column of air ranging in width from a few yards to more than a mile and whirling at speeds estimated at 300 miles (483 kilometers) an hour or higher. A tornado usually takes the form of a funnel-shaped cloud extending downward out of a cumulonimbus cloud. Where the funnel reaches the ground, it can cause enormous destruction.

The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

tornado

a highly localized, violent windstorm occurring over land, usually in the U.S. Midwest, characterized by a vertical, funnel-shaped cloud.

See also: Wind

-Ologies & -Isms. Copyright 2008 The Gale Group, Inc. All rights reserved.

tornado

An intense cyclone where the spiraling wind-speed reaches over 200 miles (320km) per hour.

Dictionary of Unfamiliar Words by Diagram Group Copyright © 2008 by Diagram Visual Information Limited

торнадо, смерч, ураган, вихрь, шквал

существительное ↓

Словосочетания

in the path of a tornado — на пути урагана  
the funnel cloud of a tornado — воронкообразное облако урагана  
tornado watch — предупреждение о возможности смерчей  
tornado cyclone — торнадообразующий циклон; торнадо  
a great tornado of applause — шквал аплодисментов; взрыв аплодисментов; буря аплодисментов  
convective tornado — конвективное торнадо  
cyclonic tornado — циклоническое торнадо  
design basic tornado — максимальный проектный ураган  
design-basis tornado — проектный торнадо  
electronic tornado — сварка электронным вихрем  
tornado of work was in her — демон деятельности вселился в нее  
tornado of work — демон деятельности  

Примеры с переводом

Примеры, ожидающие перевода

Возможные однокоренные слова

tornadic  — смерчевой, вихревой, ураганный

Формы слова

noun
ед. ч.(singular): tornado
мн. ч.(plural): tornadoes or tornado