Tornadoes develop from severe thunderstorms in warm, moist, unstable air along and ahead of cold fronts. Such thunderstorms also may generate large hail and damaging winds. When intense springtime storm systems produce large, persistent areas that support tornado development, major outbreaks can occur.

How is a tornado formed step by step?

Rising air from the ground pushes up on the swirling air and tips it over. The funnel of swirling air begins to suck up more warm air from the ground. The funnel grows longer and stretches toward the ground. When the funnel touches the ground it becomes a tornado.

What are most tornadoes caused by?

The most destructive tornadoes occur from supercells, which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone. (Supercells can also produce damaging hail, severe non-tornadic winds, frequent lightning, and flash floods.)