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Atmospheric Instability: Thunderstorms cause tornadoes. First comes instability. Instability occurs when warm, moist surface air meets cooler, dry air overhead.
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Wind Shear: Atmospheric wind speed and direction fluctuate with height. Tornadoes need high wind shear. The wind should blow in varied directions and speeds at different elevations.
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Updrafts and Rotation:Powerful updrafts of warm, moist air rise fast into cooler air above a severe thunderstorm. Wind shear rotates the updraft horizontally.
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Mesocyclone Formation: When the rotating updraft becomes organized and tightens, it forms a mesocyclone. This is a critical step in the tornado formation process.
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Tornado Funnel: The mesocyclone can stretch and tilt the revolving updraft vertically, creating a tornado funnel. Thunderstorm funnel clouds reach the ground.
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Touchdown: If the funnel cloud touches the earth, the tornado has "touched down." It becomes a tornado with damaging wind speeds.
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Tornado Lifecycle: Tornadoes can vary greatly in size, intensity, and lifespan. Some may last only a few minutes, while others can persist for hours, traveling long distances.