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Tornadoes A tornado is a swirling mass of clouds touching the ground. A tornado looks like an elephant's trunk. Tornadoes form from mammatus clouds in thunderstorms. Mammatus clouds are clouds with lumps in them caused by downdrafts. Mesocyclones are slow spinning clouds in thunderstorms. If a mesocyclone starts spinning fast enough, it may produce a tornado. Ninety percent of the world's tornadoes occur in the United States. Most tornadoes occur in the central United States. Tornadoes usually occur in late spring and summer. In the United States, about 700 tornadoes occur each year. There are six different ratings for tornadoes. These are: F0, F1, F2, F3, F4, F5. The ratings are based on the speed of the tornado and the damage they do. F0 tornadoes do light damage to chimneys, TV antennas, and roof shingles. Small tree branches can be broken. Nearly three out of every ten tornadoes are F0. Their winds are 40-72 miles per hour. F1 tornadoes have winds from 73-112 miles per hour. They can uproot trees, overturn cars, and push trailers around. About four out of every ten tornadoes are F1. F2 tornadoes have winds from 113-157 miles per hour. They can blow roofs off homes, leaving only strong walls standing. They demolish sheds and small outbuildings. They cause wooden buildings to collapse. About two or three out of every ten tornadoes are F2. F3 tornadoes have winds from 158-206 miles per hour. They can flatten all the trees in a forest and collapse metal buildings. They blow off roofs and tumble exterior walls made of concrete. Six out of every hundred tornadoes are F3. F4 tornadoes have wind speeds of 207-260 miles per hour. They will leave few, if any walls standing. They can pluck trees from their roots and break their trunks in half. They can pick up large building materials and hurl them with such force that they penetrate concrete. Two out of every hundred tornadoes are F4. F5 tornadoes have winds over 261 miles per hour. They make the land look like a bulldozer ran over it. One out of every hundred tornadoes are rated F5. A tornado's wind's top speed is about 300 miles per hour, although it only travels around 60 miles an hour across land. Sometimes tornadoes form over water. They are called waterspouts. Waterspouts are not as big as tornadoes that form on land, and they are weaker. Sometimes waterspouts pick up fish and frogs and drop them on land. Tornadoes are a powerful and amazing force. They can flatten whole forests and blow buildings apart. They can pick up objects from the ground, bring them high up in the air, and set them down in another place. Tornadoes are awesome!
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