Tornado

A tornado is a spinning column of air that reaches from a thunderstorm down to the ground. Tornadoes are one of the most powerful kinds of weather on Earth. They can lift cars, tear roofs off houses, and snap trees in half. Most tornadoes last only a few minutes, but the damage they cause can stretch for miles.

Tornadoes form during big thunderstorms called supercells. Inside a supercell, warm wet air rises fast while cold dry air sinks. When winds at different heights blow in different directions, the air starts to spin. At first the spinning is sideways, like a tube rolling in the sky. Rising air can tilt the tube upright. If the spinning column reaches the ground, it becomes a tornado.

A tornado looks like a dark funnel hanging from the clouds. The funnel is made of water droplets, dust, and dirt picked up by the wind. The wind itself is invisible. Tornadoes can be skinny ropes only a few feet wide, or huge wedges more than a mile across.

Scientists rate tornadoes on the Enhanced Fujita Scale, or EF Scale. It runs from EF0 to EF5. An EF0 has winds of 65 to 85 miles per hour and snaps small branches. An EF5 has winds over 200 miles per hour and can wipe entire houses off their foundations. About 7 out of 10 tornadoes are weak ones at EF0 or EF1.

The United States has more tornadoes than any other country. About 1,200 happen there each year. Most form in a wide area of the central states known as Tornado Alley, which includes Texas, Oklahoma, Kansas, and Nebraska. Warm air from the Gulf of Mexico meets cold air from Canada there, and the clash creates perfect conditions for supercells.

Some questions about tornadoes are still open. Scientists do not fully understand why some supercells make tornadoes while others, with very similar conditions, do not. Researchers chase storms in special trucks loaded with radar to study the moment a tornado forms. The newest radars can spot the tiny spin inside a thunderstorm before a funnel even reaches the ground.

If a tornado warning is issued, the safest place is a basement or a small inside room with no windows, like a bathroom or closet. Crouch low and cover your head. Mobile homes and cars are very dangerous in tornadoes. The whole storm may pass overhead in less than a minute, but that minute is one of the most powerful things our planet can do.