Tornadoes form from large thunderstorms called super cells. Meteorologists are not quite sure what causes some storms to produce tornadoes while others do not. What is known is that there is circulation inside of a thunderstorm. Warm air rises up and cools with altitude until it becomes unstable and descends again. This rotation generally happens parallel to the ground and produces nothing more than rain, hail, and lightning.

If the storm twists and the rotation becomes perpendicular to the ground, a tornado can form. Officially, to be labeled a tornado the rotating column must be in contact with the ground and the storm cloud.