http://www.livescience.com/3589-12-twisted-tornado-facts.html

Tornado sites/videos

http://www.weather.com/encyclopedia/tornado/forecast.html

http://www.weather.com/encyclopedia/tornado/forecast.html

http://tornado-facts.com

http://www.cnn.com/2013/05/20/us/tornadoes-fast-facts/

http://www.sciencekids.co.nz/sciencefacts/weather/tornado.html