What factors create big tornado outbreaks?

January 23, 2009 11:02:29 AM PST
Big tornado outbreaks result from thunderstorms called "supercells".

Erica's Answer:

Sometimes, these supercells, which look like huge, round clouds on satellite imagery, can be as big as the state of Pennsylvania! Big supercells form in the Midwest and Southeast where the land is flat and the warm, moist air from the Gulf of Mexico has an unobstructed path.

Supercell thunderstorms form when warm, moist air from the Gulf rushes northward and collides with cooler, drier air that has pushed south from Canada. When the jet stream is directly over this collision, it further enhances the development of thunderstorms. This environment is most conducive to supercells.

Most tornadoes in supercell storms are found in the southwestern segment of the supercell. Tornadoes can develop frequently, in multiples, and in quick sequence in supercell thunderstorms.

- Erica