A tornado is a violent, dangerous, rotating column of air which is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. Tornadoes come in many 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 between 40 mph (64 km/h) and 110 mph (177 km/h), are approximately 250 feet (75 m) across, and travel a few miles (several kilometers) before dissipating. Some attain wind speeds of more than 300 mph (480 km/h), stretch more than a mile (1.6 km) across, and stay on the ground for dozens of miles (more than 100 km).Although tornadoes have been observed on every continent except Antarctica, most occur in the United States. They also commonly occur in southern Canada, south-central and eastern Asia, east-central South America, Southern Africa, northwestern and southeast Europe, western and southeastern Australia, and New Zealand.
1 Etymology
2 Definitions
2.1 Tornado
2.2 Funnel cloud
2.3 Tornado family
2.4 Tornado outbreak
3 Types
3.1 True tornadoes
3.1.1 Multiple vortex tornado
3.1.2 Satellite tornado
3.1.3 Waterspout
3.1.4 Landspout
3.2 Tornado-like circulations
3.2.1 Gustnado
3.2.2 Dust devil
3.2.3 Fire whirl
3.2.4 Steam devil
4 Characteristics
4.1 Shape
4.2 Size
4.3 Appearance
4.4 Rotation
4.5 Sound and seismology
4.6 Electromagnetic, lightning, and other effects
5 Life cycle
5.1 Supercell relationship
5.2 Formation
5.3 Maturity
5.4 Demise
6 Intensity and damage
7 Climatology
7.1 Associations with climate and climate change
8 Prediction
8.1 Australia
8.2 Europe
8.3 United Kingdom
8.4 United States
8.5 Other areas
9 Detection
9.1 Storm spotting
9.1.1 Visual evidence
9.2 Radar
10 Extremes
11 Safety
12 Myths and misconceptions
13 Continuing research
14 See also
15 References
16 Further reading
17 External links
//
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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. A tornado is also commonly referred to as a twister, and is also sometimes referred to by the old-fashioned colloquial term cyclone. 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 film Twister.
Definitions
A tornado near Seymour, Texas
This tornado has no funnel cloud, however, the rotating dust cloud indicates that strong winds are occurring at the surface, and thus it is a true tornado. This picture was taken in Louisville, Kentucky.
Tornado
The Glossary of Meteorology defines a tornado as "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..."[9] In practice, 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. "Tornado" refers to the vortex of wind, not the condensation cloud.
Funnel cloud
Main article: funnel cloud
A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds (see 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.
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 including most tornadoes under this definition. Among many meteorologists, a funnel cloud is strictly defined as a rotating cloud which is not associated with strong winds at the surface, and a "condensation funnel" is a broad term for any rotating cloud below a cumuliform cloud.
Tornadoes often begin as funnel clouds with no associated strong winds at the surface, however, not all of these 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.
Tornado family
Main article: tornado family
Occasionally, a single storm will produce more than one tornado, either simultaneously or in succession. Multiple tornadoes produced by the same storm are referred to as a tornado family.
Tornado outbreak
Main articles: tornado outbreak and tornado outbreak sequence
Occasionally, several tornadoes are 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.
Types
A multiple-vortex tornado outside of Dallas, Texas on April 2, 1957
True tornadoes
Multiple vortex tornado
Main article: multiple vortex tornado
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.
Satellite tornado
A satellite tornado is a term for 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 funnel, and is much smaller than the main funnel.
Waterspout
A waterspout near the Florida Keys
Main article: waterspout
A waterspout is defined by the National Weather Service simply 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 in dynamics to dust devils and landspouts. They form at the bases of cumulus congestus cloud towers in tropical and semitropical waters. They have relatively weak winds, smooth laminar walls, and typically travel very slowly, if at all. They occur most commonly in the Florida Keys and in the northern Adriatic Sea.
Tornadic waterspouts are more literally "tornadoes over water". They can form over water like mesocyclonic tornadoes, or be a land tornado which crosses onto water. Since the
y form from severe thunderstorms and can be far more intense, faster, and longer-lived than fair weather waterspouts, they are considered far more dangerous.
Landspout
A landspout near North Platte, Nebraska on May 22, 2004
Main article: landspout
A landspout (officially known as a dust-tube tornado) is a tornado not associated with a mesocyclone. The name stems from their characterization as essentially 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 ground. 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 still produce strong winds and may cause serious damage.
Tornado-like circulations
Gustnado
Main article: gustnado
A gustnado (gust front tornado) is a small, vertical swirl associated with a gust front or downburst. Because they are technically not associated with the cloud base, there is some debate as to whether or not gustnadoes are actually 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 horizontally (or diagonally) and make contact with the ground. The result is a gustnado. They usually cause small areas of heavier rotational wind damage among areas of straight-line wind damage. It is also worth noting that since they are absent of any Coriolis influence from a mesocyclone, they seem to be alternately cyclonic and anticyclonic without preference.
Dust devil
A dust devil in Nevada
Main article: 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 rarely as strong as even 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 actual cloud. However, they can, on occasion, result in major damage, especially in arid areas.
Fire whirl
Main article: fire whirl
Tornado-like circulations occasionally occur near large, intense wildfires and 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. However, they can produce significant damage.
Steam devil
Main article: steam devil
A steam devil is a term describing a rotating updraft that involves steam or smoke. A steam devil is very rare, but they mainly form from smoke emitting from a power plant smokestack. Hot springs and deserts may also be suitable locations for a steam devil to form. There have also been reports of cold air steam devils as well.
Most tornadoes have wind speeds between 40 mph (64 km/h) and 110 mph (177 km/h), are approximately 250 feet (75 m) across, and travel a few miles (several kilometers) before dissipating. Some attain wind speeds of more than 300 mph (480 km/h), stretch more than a mile (1.6 km) across, and stay on the ground for dozens of miles (more than 100 km).Although tornadoes have been observed on every continent except Antarctica, most occur in the United States. They also commonly occur in southern Canada, south-central and eastern Asia, east-central South America, Southern Africa, northwestern and southeast Europe, western and southeastern Australia, and New Zealand.
1 Etymology
2 Definitions
2.1 Tornado
2.2 Funnel cloud
2.3 Tornado family
2.4 Tornado outbreak
3 Types
3.1 True tornadoes
3.1.1 Multiple vortex tornado
3.1.2 Satellite tornado
3.1.3 Waterspout
3.1.4 Landspout
3.2 Tornado-like circulations
3.2.1 Gustnado
3.2.2 Dust devil
3.2.3 Fire whirl
3.2.4 Steam devil
4 Characteristics
4.1 Shape
4.2 Size
4.3 Appearance
4.4 Rotation
4.5 Sound and seismology
4.6 Electromagnetic, lightning, and other effects
5 Life cycle
5.1 Supercell relationship
5.2 Formation
5.3 Maturity
5.4 Demise
6 Intensity and damage
7 Climatology
7.1 Associations with climate and climate change
8 Prediction
8.1 Australia
8.2 Europe
8.3 United Kingdom
8.4 United States
8.5 Other areas
9 Detection
9.1 Storm spotting
9.1.1 Visual evidence
9.2 Radar
10 Extremes
11 Safety
12 Myths and misconceptions
13 Continuing research
14 See also
15 References
16 Further reading
17 External links
//
Part of the Nature series onWeather
Seasons
Temperate
Spring · SummerAutumn · Winter
Tropical
Dry seasonWet season
Storms
Thunderstorm · TornadoTropical cyclone (Hurricane)Extratropical cycloneWinter storm · BlizzardFog · Ice storm
Precipitation
Drizzle · Rain · SnowFreezing rain · Ice pelletsHail · Graupel
Topics
MeteorologyWeather forecastingClimate · Air pollution
Weather Portal
v • d • e
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. A tornado is also commonly referred to as a twister, and is also sometimes referred to by the old-fashioned colloquial term cyclone. 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 film Twister.
Definitions
A tornado near Seymour, Texas
This tornado has no funnel cloud, however, the rotating dust cloud indicates that strong winds are occurring at the surface, and thus it is a true tornado. This picture was taken in Louisville, Kentucky.
Tornado
The Glossary of Meteorology defines a tornado as "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..."[9] In practice, 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. "Tornado" refers to the vortex of wind, not the condensation cloud.
Funnel cloud
Main article: funnel cloud
A tornado is not necessarily visible; however, the intense low pressure caused by the high wind speeds (see 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.
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 including most tornadoes under this definition. Among many meteorologists, a funnel cloud is strictly defined as a rotating cloud which is not associated with strong winds at the surface, and a "condensation funnel" is a broad term for any rotating cloud below a cumuliform cloud.
Tornadoes often begin as funnel clouds with no associated strong winds at the surface, however, not all of these 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.
Tornado family
Main article: tornado family
Occasionally, a single storm will produce more than one tornado, either simultaneously or in succession. Multiple tornadoes produced by the same storm are referred to as a tornado family.
Tornado outbreak
Main articles: tornado outbreak and tornado outbreak sequence
Occasionally, several tornadoes are 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.Types
A multiple-vortex tornado outside of Dallas, Texas on April 2, 1957
True tornadoes
Multiple vortex tornado
Main article: multiple vortex tornado
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.
Satellite tornado
A satellite tornado is a term for 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 funnel, and is much smaller than the main funnel.
Waterspout
A waterspout near the Florida Keys
Main article: waterspout
A waterspout is defined by the National Weather Service simply 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 in dynamics to dust devils and landspouts. They form at the bases of cumulus congestus cloud towers in tropical and semitropical waters. They have relatively weak winds, smooth laminar walls, and typically travel very slowly, if at all. They occur most commonly in the Florida Keys and in the northern Adriatic Sea.
Tornadic waterspouts are more literally "tornadoes over water". They can form over water like mesocyclonic tornadoes, or be a land tornado which crosses onto water. Since the
y form from severe thunderstorms and can be far more intense, faster, and longer-lived than fair weather waterspouts, they are considered far more dangerous.Landspout
A landspout near North Platte, Nebraska on May 22, 2004
Main article: landspout
A landspout (officially known as a dust-tube tornado) is a tornado not associated with a mesocyclone. The name stems from their characterization as essentially 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 ground. 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 still produce strong winds and may cause serious damage.
Tornado-like circulations
Gustnado
Main article: gustnado
A gustnado (gust front tornado) is a small, vertical swirl associated with a gust front or downburst. Because they are technically not associated with the cloud base, there is some debate as to whether or not gustnadoes are actually 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 horizontally (or diagonally) and make contact with the ground. The result is a gustnado. They usually cause small areas of heavier rotational wind damage among areas of straight-line wind damage. It is also worth noting that since they are absent of any Coriolis influence from a mesocyclone, they seem to be alternately cyclonic and anticyclonic without preference.
Dust devil
A dust devil in Nevada
Main article: 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 rarely as strong as even 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 actual cloud. However, they can, on occasion, result in major damage, especially in arid areas.
Fire whirl
Main article: fire whirl
Tornado-like circulations occasionally occur near large, intense wildfires and 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. However, they can produce significant damage.
Steam devil
Main article: steam devil
A steam devil is a term describing a rotating updraft that involves steam or smoke. A steam devil is very rare, but they mainly form from smoke emitting from a power plant smokestack. Hot springs and deserts may also be suitable locations for a steam devil to form. There have also been reports of cold air steam devils as well.
