Fujita Tornado Damage Scale

The most destructive tornadoes form from rotating thunderstorms called supercells, which also can produce damaging hail, frequent lightning, and heavy rain. But not every thunderstorm spawns a tornado. Scientists still don't fully understand the process, according to the National Weather Service.

Tornadoes are rated on the Fujita scale based on estimated wind speeds and damage.

The ratings are:

F0: Winds less than 73 mph. Light damage, including broken tree branches, damaged sign boards, some damage to chimneys.

(Copyright 2005 by The Associated Press.  All Rights Reserved.)