Kids of all ages can't help by be interested in the awesome destructive power of a tornado. Simple Schooling Thunderstorms is a nice lengthy unit that is divided in into manageable chunks so they don't get bored. In addition, there are many interactivities to keep them excited about science. Don't forget to have them do all the other earth science units too!
If there are links within the course they may click them as they come up - OR they can return to this page and access them here. In addition, there are suggested supplemental activities listed below that they can do afterward. Some units have optional pdf files and worksheets that can be found on the printables page.
Tornado Interactive Unit Study
Anatomy of a Killer
Visualize Tornado Formation
Tornado Animation (BBC)
Tornado Visualization 2 (Better!)
(Turn the volume down for this one below - the panicked guy says something that might be offensive)
Ditto for volume on this one - they have the radio up really loud!