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.
See photos of Samaras's work. All rights reserved. Although this spinning column of air starts out horizontal, it can easily go vertical and drop down out of the cloud. When it touches the ground, it's a tornado. The winds inside the spinning column of some tornadoes are the fastest of any on Earth. They have been clocked at over miles per hour! Sometimes the spinning column of air lifts off the ground, then touches down again some distance along its path. It's hard to measure the winds in a tornado directly.
So they are evaluated by the amount of damage they do. Here is a scale meteorologists use to describe tornado intensity based on damage. These satellites can more quickly monitor the motion of clouds to identify a severe storm as soon as it develops. They are also better at understanding what's actually going on inside the cloud: what characteristics the cloud has that indicate a severe storm and how much lightning it produces. All these measurements affect how likely the cloud is to produce a tornado.
The most violent tornadoes are capable of tremendous destruction with wind speeds of up to mph. They can destroy large buildings, uproot trees and hurl vehicles hundreds of yards. They can also drive straw into trees. Damage paths can be in excess of one mile wide to 50 miles long. In an average year, tornadoes are reported nationwide. How do tornadoes form? Most tornadoes form from thunderstorms. This happens when air in the storm sinks to the ground and spreads out across the land in gusts.
Gusts of warmer air rise as they blow. Gusts of cooler air sink as they blow across the land. If there are enough rising and sinking gusts, the air near the ground starts spinning. This happens in the same way that figure skaters spin faster when their arms are drawn in rather than when their arms are outstretched.
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