How do tornadoes form? Most tornadoes form from thunderstorms. You need warm, moist air from the Gulf of Mexico and cool, dry air from Canada. When these two air masses meet, they create instability in the atmosphere. A change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere. Rising air within the updraft tilts the rotating air from horizontal to vertical.
An area of rotation, miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.
Enhanced, Operational Fujita Scale. What makes a cloud create one of these powerful assaults to Earth's surface? How is it that a violent whirlwind can form in a cloud and then reach to the ground and make splinters and chaos of everything in its path? On average, the U. A ten-state area of the Midwest has been named "Tornado Alley" in recognition of its attractiveness to tornadoes.
However, tornadoes can occur in any state. In , Alabama was struck particularly hard, with tornadoes rated EF-5 the most intense on the Enhanced Fujita scale hitting Hacklesburg and Birmingham. Imagery from GOES enabled weather forecasters to foresee the trouble that was about to hit Alabama.
Click image for animation. With most weather events, even hurricanes, you know what to expect. The weather forecast will give you a few hours' warning and some idea of what is coming.
This information is thanks partly to hard-working satellites that keep a constant eye on the weather. However, predicting tornadoes precisely is a different story. One minute it's just raining or hailing, and the next minute the roof or even the whole house is gone. If you were lucky, you and your family had a few seconds to find some shelter where you would not be picked up by the violent winds or seriously injured by large chunks of flying debris.
Where do these violent and unpredictable storms come from? 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. This is called conservation of angular momentum. The rotating air moves horizontally across the land, and can be tilted vertically by the force of the rising, rotating air.
That allows a tornado to form. Most tornadoes form during supercell thunderstorms, but not all supercell thunderstorms produce tornadoes.
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