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| | Tornadoes |
 | | Tornadoes are most often spawned by giant thunderstorms known as "supercells." These powerful, highly organized storms form when warm, moist air along the ground rushes upward, meeting cooler, drier air. |
 | | The conditions that lead to the formation of tornadoes are most often met in the central and southern U.S., where warm, humid air from the Gulf of Mexico collides with cool, dry air from the Rockies and Canada. |
 | | This area, dubbed "tornado alley," extends roughly from the Rocky Mountains to the Appalachians, and from Iowa and Nebraska to the Gulf of Mexico. |
| www.factmonster.com /spot/tornado1.html (444 words) |
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