The funnel continues to grow and eventually it descends from the cloud. When it touches the ground, it becomes a tornado. Twisters are usually accompanied or preceded by severe thunderstorms and high wlnds. Hail is also common. Once a tornado hits the ground, it may live for as little as a few seconds or as long as three hours.
The average twister is about feet wide and moves about 30 miles an hour. Most don't travel more than six miles before dying out. Massive tornadoes, however—the ones capable of widespread destruction and many deaths—can roar along as fast as miles an hour. These measurements are scientists' best estimations. Anemometers, which measure wind speed, cannot withstand the enormous force of tornadoes to record them.
Using units F0 to F5, the Fujita scale measures a tornado's intensity by analyzing the damage the twister has done and then matching that to the wind speeds estimated to produce comparable damage. The United States now uses the EF Enhanced Fujita scale , which takes more variables into account when assigning wind speeds to a tornado. Every year in the United States, tornadoes do about million dollars in damage and kill about 70 people on average.
Extremely high winds tear homes and businesses apart. Winds can also destroy bridges, flip trains, send cars and trucks flying, tear the bark off trees, and suck all the water from a riverbed. High winds sometimes kill or injure people by rolling them along the ground or dropping them from dangerous heights.
But most tornado victims are struck by flying debris—roofing shingles, broken glass, doors, metal rods. The number of average deaths per year in the United States used to be higher before improved forecasting and warning systems were put into place.
Meteorologists at the U. National Weather Service use Doppler radar, satellites, weather balloons, and computer modeling to watch the skies for severe storms and tornadic activity. Doppler radars record wind speeds and identify areas of rotation within thunderstorms. Since Doppler radar has been in use, the warning time for tornadoes has grown from fewer than five minutes in the s to an average of 13 minutes by the late s.
A supercell thunderstorm strikes in South Dakota. Among the most severe storms, supercells can bring strong winds, hail, and even tornadoes.
See more extreme weather pictures. When weather conditions are conducive for tornado formation, the National Weather Service issues a tornado watch. When a tornado has been sighted or indicated on radar, a tornado warning is issued. Some scientists, meteorology buffs, and adrenaline junkies hit the road during tornado season to chase storms. Researchers race to place sensors in tornadoes' paths. The sensors measure data such as wind speed, barometric pressure, humidity, and temperature.
The challenge for researchers is being in the right place at the right time. Every morning they study weather conditions and head for the area that seems most likely to spawn a twister. They drive through severe storms, dodge lightning, face flash floods, and get pounded by hail—sometimes for years—before ever spotting a tornado. All at considerable risk. In , National Geographic Explorer Tim Samaras and his team were killed while trying to study a tornado in Oklahoma.
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Learn more about how FutureLearn is transforming access to education. Learn more about this course. How are tornadoes formed? This Met Office video explains the phases in the formation of a tornado. In some cases, it is also possible to detect the flying debris created by a tornado with radar. Ordinary citizen volunteers make up what is called the SKYWARN network of storm spotters, who work with their local communities to watch for approaching tornadoes, so those communities can take appropriate action in the event of a tornado.
Spotter information is relayed to the National Weather Service. You can be a storm spotter too! Visit www. If your area is not listed, contact your local National Weather Service Office. How do tornadoes form? See our explanation in the Tornado Types section. Can tornadoes be predicted? Yes, but only to a limited extent. Although the process by which tornadoes form is not completely understood, scientific research has revealed that tornadoes usually form under certain types of atmospheric conditions.
When forecasters see those conditions, they can predict that tornadoes are likely to occur. However, it is not yet possible to predict in advance exactly when and where they will develop, how strong they will be, or precisely what path they will follow.
Once a tornado is formed and has been detected, warnings can be issued based on the path of the storm producing the tornado, but even these cannot be perfectly precise about who will or will not be struck. What are the people called who study tornadoes? People who study tornadoes are just research meteorologists or atmospheric scientists. You may have heard another term—storm chaser—but that really refers to people who chase tornadoes and storms for a hobby.
Research meteorologists have a scientific purpose behind their pursuit of severe weather. They have to come up with questions they think they can answer by taking certain measurements. What are the wind speeds in a tornado? We're not really sure what the highest wind speed might be inside a tornado, since strong and violent tornadoes destroy weather instruments.
We really only have measurements of the winds inside weaker tornadoes. How fast do tornadoes move? We don't have detailed statistics about this. Movement can range from almost stationary to more than 60 mph. A typical tornado travels at around 10—20 miles per hour. How long is a tornado usually on the ground?
Detailed statistics about the time a tornado is on the ground are not available. This time can range from an instant to several hours. The average is about five minutes.
The movie Twister was based upon work NSSL did in the mids using a gallon drum outfitted with various meteorological sensors. NSSL tried for several years to put it in the path of an oncoming tornado, but had minimal success. It is possible that the technology could exist someday; however there are significant challenges with observations such as these.
Read more about Twister science Has every state had a tornado? Yes, although some states have many more tornadoes than others. Are there tornadoes in the Arctic Circle? We are not aware of any tornadoes occurring in the Arctic Circle.
Tornadoes need moisture and warm air to form, which is unusual at that latitude. Plus tornadoes or their evidence have to be observed by someone, and the Arctic Circle has few residents! Do tornadoes really stay away from gullies, rivers and mountains?
A gully could actually make a tornado more intense, just as an ice skater spins faster when he or she stands up tall and stretches their arms up straight over their heads. Every major river east of the Rockies has been crossed by a significant tornado, and high elevations in the Appalachians, Rockies, and Sierra Nevada have all experienced tornadoes. Do tornadoes always come from a wall cloud? A wall cloud is not always present. It is also possible that you cannot see a wall cloud because of your viewing angle or low level clouds.
What does a tornado sound like? People who have been in a tornado say it sounds like a jet engine or a freight train and is very loud. They said it hurt their ears, but they were more worried about what might happen to them than they were about the pain in their ears.
Can tornadoes be stopped? You have to consider that the tornado is part of something bigger: the supercell thunderstorm. Unless you disrupt the supercell thunderstorm itself, you would likely have another tornado, even if you were able to destroy the first.
The thunderstorm's energy is much greater than the tornado. No one has tried to disrupt the tornado because the methods to do so could likely cause even more damage than the tornado.
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