Tornado facts for kids

Quick facts for kids Tornado
An F3 tornado near Anadarko, Oklahoma, 1999.
Season	Primarily spring and summer, but can be at any time of year
Effect	Wind damage

A tornado is a tube of violently spinning air that touches the ground. Wind inside the tornado spins fast, but the actual 'circle' of wind around them is huge. This makes tornadoes very dangerous. Tornadoes are especially dangerous to people in cars or mobile homes. About 60 people are killed by tornadoes every year.

Tornadoes destroy things. They can tear houses to pieces and often leave people homeless. They are smaller than hurricanes but stronger. Nearly three quarters of the world's tornadoes happen in the United States. However, they can happen anywhere.

They cause a lot of damage to anything in their path. Tornadoes are ranked on the Enhanced Fujita scale, from EF0 to EF5. EF0 for tornados that caused the least damage, and EF5 for the ones that caused the most.

Tornadoes can happen in nearly any part of the world. In the United States, a tornado has happened in all states. The middle part of the United States is nicknamed 'Tornado Alley' for the number of tornadoes there. A tornado can have wind speeds of over 300 miles per hour (480 km/h).

Most tornadoes have wind speeds less than 110 miles per hour (180 km/h), are about 250 feet (80 m) across and travel a few miles before disappearing. Other tornado-like phenomena that exist in nature include the gustnado, dust devil, fire whirls, and steam devil; downbursts are frequently confused with tornadoes, though their action is not similar.

How they form

Composite of eight images shot in sequence as a tornado formed in Kansas in 2016

A sequence of images showing the birth of a tornado. First, the rotating cloud base lowers. This lowering becomes a funnel, which continues descending while winds build near the surface, kicking up dust and debris and causing damage. As the pressure continues to drop, the visible funnel extends to the ground. This tornado, near Dimmitt, Texas, was one of the best-observed violent tornadoes in history.

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.

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.

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.

Maturity

The mature stage of a tornado that occurred in Union City, Oklahoma on May 24, 1973.

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. 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. 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.

Dissipation

A tornado dissipating or "roping out" in Eads, CO.

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. 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.

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.

Characteristics

Condensation funnel

A tornado does not necessarily need to be visible; however, the extremely low pressure caused by the high wind speeds and rapid rotation usually causes water vapor in the air to condense into a visible condensation funnel. The tornado is the vortex of wind, not the condensation cloud.

Tornado family

A single storm may produce multiple tornadoes and mesocyclones. Tornadoes produced from the same storm are referred to as a tornado family. Sometimes multiple tornadoes from distinct mesocyclones occur at the same time.

Occasionally, several tornadoes are spawned from the same very large storm. If there is no break in their 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.

Sometimes, tornadoes happen in groups. 148 tornadoes struck on the same day in April 1974. Many towns in the midwestern United States and Canada were destroyed. More than 300 people died. They were hit by flying wrecks, buried under houses, and thrown by powerful winds. That day, students in Xenia, Ohio were practicing for a play on the auditorium stage. One girl looked out the window and saw the tornado. The students ran into the hall, covering their heads. A few seconds later, all the school buses flew right onto the stage.

A man in another town hid under the couch in his living room. He held onto one couch leg. The tornado struck his house, and winds blew around him. When the tornado left, he was outside. There was no house. The couch had disappeared, and he was only holding onto one couch leg.

Damage scale

The Fujita scale and the Enhanced Fujita Scale rate tornadoes by how much damage they cause. The Enhanced Fujita (EF) Scale was an update to the older Fujita scale. The updated scale uses engineered wind estimates and has better damage descriptions. The EF Scale was designed so that a tornado rated on the Fujita scale would get the same numerical rating, and was used in the United States since 2007. An EF0 tornado will probably damage trees but not big buildings, whereas an EF5 tornado can rip buildings off their foundations leaving them destroyed and even damage big skyscrapers.

In the United States, 80% of tornadoes are EF0 and EF1 (T0 through T3) tornadoes. Less than 1% of tornadoes are violent tornadoes (EF4, T8 or stronger).

Tornado watches/warnings/emergencies

A "tornado watch" is given when the weather conditions look like a tornado could form. A 'PDS (Particularly Dangerous Situation)' watch is given when a likely tornado outbreak is to start, many strong tornadoes will form in the area, or an ongoing tornado outbreak is in the works in the area. A "tornado warning" is given if somebody has actually seen a tornado or if a tornado 'signature' (usually the storm has a 'hook' or 'U' echo) has shown up on radar. Tornado emergencies are issued in Special Weather Statements or Tornado Warnings saying that a powerful tornado is about to hit an area with a lot of people in it (especially cities in Tornado Alley), a tornado has been spotted, and the tornado is expected to cause deaths.

Myths and misconceptions

The 1999 Salt Lake City tornado disproved several misconceptions, including the idea that tornadoes cannot happen in cities.

It is often thought that opening windows will lessen the damage caused by a tornado. While there is a big drop in atmospheric pressure inside a strong tornado, it is unlikely that the pressure drop would be enough to cause the house to explode. Opening windows may actually increase the tornado's damage. A violent tornado can destroy a house whether its windows are open or closed. Another common misconception is that highway overpasses provide adequate shelter from tornadoes. Due to the Venturi effect, tornadic winds are stronger in the small space of an overpass. In the 1999 Oklahoma tornado outbreak of May 3, 1999, three highway overpasses were directly hit by tornadoes. At each of the three places there was a death, along with many life-threatening injuries. 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.

There are areas which people believe to be safe from tornadoes, whether by being in a city, near a major river, hill, or mountain, or even protected by supernatural forces. Tornadoes have been known to cross major rivers, climb mountains, hit valleys, and have damaged several city centers. As a general rule, no area is safe from tornadoes, though some areas are more likely to be hit than others.

Safety tips

To keep safe in a tornado, here are some tips you can follow:

• Go to the lowest floor of the building. Stay close to the center of the building and away from windows, for example, a bathroom with no windows and get into the bathtub.
• Find a piece of strong furniture or a mattress to go under or hide in a closet and wait until it is over.
• If you are in a school, do not go to the gymnasium or any other place that has a high ceiling. Squat near the wall, placing your hands on the back of your head.
• If you cannot find shelter, find the lowest, most protected ground and cover your head with your hands.
• Do not drive in tornadoes. If you are in your car, position your head above the steering wheel, and cover yourself up.
• Do not seek shelter underneath an underpass or a bridge, as winds can send debris in your path.

Related pages

• Waterspout
• Steam devil
• Tornado drill

Images for kids

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  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.

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  A wedge tornado, nearly a mile wide, which hit Binger, Oklahoma in 1981

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  Photographs of the Waurika, Oklahoma tornado of May 30, 1976, taken at nearly the same time by two photographers. In the top picture, the tornado is lit by the sunlight focused from behind the camera, thus the funnel appears bluish. In the lower image, where the camera is facing the opposite direction, the sun is behind the tornado, giving it a dark appearance.

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  An illustration of generation of infrasound in tornadoes by the Earth System Research Laboratory's Infrasound Program

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  A waterspout near the Florida Keys in 1969.

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  A dust devil in Arizona

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  A house displaying EF1 damage. The roof and garage door have been damaged, but walls and supporting structures are still intact.

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  Areas worldwide where tornadoes are most likely, indicated by orange shading

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  Intense tornado activity in the United States. The darker-colored areas denote the area commonly referred to as Tornado Alley.

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  Path of a tornado across Wisconsin on August 21, 1857

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  A Doppler on Wheels radar loop of a hook echo and associated mesocyclone in Goshen County, Wyoming on June 5, 2009. Strong mesocyclones show up as adjacent areas of yellow and blue (on other radars, bright red and bright green), and usually indicate an imminent or occurring tornado.

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  A rotating wall cloud with rear flank downdraft clear slot evident to its left rear

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  A map of the tornado paths in the Super Outbreak (April 3–4, 1974)

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  Damage from the Birmingham tornado of 2005. An unusually strong example of a tornado event in the United Kingdom, the Birmingham Tornado resulted in 19 injuries, mostly from falling trees.

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  A Doppler on Wheels unit observing a tornado near Attica, Kansas

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  A tornado that occurred at Seymour, Texas in April 1979

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  F4 tornado in Roanoke, Illinois on July 13, 2004

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  he mature stage of a tornado that occurred in Union City, Oklahoma on May 24, 1973

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  A radar reflectivity image of a classic tornadic supercell near Oklahoma City, Oklahoma on May 3, 1999

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  EF4 tornado near Marquette, Kansas on April 14, 2012

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

See also

In Spanish: Tornado para niños