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Tornadoes - Coggle Diagram
Tornadoes
How It Forms
Tornadoes form when warm, humid air collides with cold, dry air.
The denser cold air is pushed over the warm air, usually producing thunderstorms.
The warm air rises through the colder air, causing an updraft.
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As the rotating updraft, called a mesocycle, draws in more warm air from the moving thunderstorm, its rotation speed increases.
Cool air fed by the jet stream, a strong band of wind in the atmosphere, provides even more energy.
Water droplets from the mesocyclone's moist air form a funnel cloud. The funnel continues to grow and eventually it descends from the cloud. When it touches the ground, it becomes a tornado.
What Is It
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It's often portended by a dark, greenish sky. Black storm clouds gather.
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A funnel suddenly appears, as though descending from a cloud. The funnel hits the ground and roars forward with a sound like that of a freight train approaching. The tornado tears up everything in its path.
What Causes It
Tornadoes can occur at any time of year, but they are more common during a distinct season that begins in early spring for the states along the Gulf of Mexico.
The season follows the jet stream—as it swings farther north, so does tornado activity.
May generally has more tornadoes than any other month, but April's twisters are sometimes more violent. Farther north, tornadoes tend to be more common later in summer.
Although they can occur at any time of the day or night, most tornadoes form in the late afternoon. By this time the sun has heated the ground and the atmosphere enough to produce thunderstorms.
Destruction
Every year in the United States, tornadoes do about 400 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.