tornado
tornadoes
tornadoes and weather
forecasting tornadoes
Fujita scale
tornado formation
tornado alley
http://www.ozsaferooms.com/kidzkorner.html
http://www.theweatherchannelkids.com/weather-ed/weather-encyclopedia/tornadoes/
This is a set of links and lesson plans provides information on tornadoes, tornado formation, and the Fujita Scale.
http://www.youtube.com/watch?v=43VoMesUd2Q