Students are first show photos of tornado damage. Recently, the Oklahoma tornado is a good source at CNN.
http://whyfiles.org/013tornado/3.html
Using the whyfiles page above, students record the pressure differential and compare that to the wind speed and F scale using a simple spreadsheet. When graphing the columns, it becomes quite clear that slight changes in pressure differential creates large changes in wind speed.
http://www.cnn.com/2013/05/22/us/gallery/oklahoma-belongings/index.html?hpt=hp_t2
Next, students are re-directed to another YouTube video of a destructive tornado.
