Tornadoes are violently rotating columns of air that extend between clouds and the ground. They can form when warm, moist air meets cold air, creating thunderstorms with the potential to produce tornadoes. Tornado strength is measured using the Enhanced Fujita Scale from EF0 to EF5 based on wind speed and damage caused. Tornado Alley in the central United States experiences most tornadoes during spring and summer. When a tornado watch is issued, tornadoes may form, while a warning means a tornado has been sighted and people should take shelter immediately.
5. Enhanced Fujita Scale http://en.wikipedia.org/wiki/Enhanced_Fujita_Scale Scale Wind Speed (MPH) Damage Caused EF0 65-85 Roof lightly damaged, broken tree branches EF1 86-110 Mobile homes turned over and roofs severely damaged EF2 111-135 Roofs torn off and trees uprooted EF3 136-165 Levels of homes destroyed and cars picked up ad thrown EF4 166-200 Houses completely destroyed EF5 >200 Reinforced concrete very damaged
![What is a Tornado? ,[object Object],http://www.weather.com/ready/tornado/index.html](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)