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Want to make your own tornado machine but you're too lazy to hunt down all the parts? $120 buys you this neat Tornado Simulator Kit, which comes with building instructions, experiment ideas, and all the parts you'll need to get going except an ultrasonic humidifier. If you don't have one already the site will sell you a humidifier for $49.95, but there are better deals online.

Tornado Simulator Kit [Science Kit & Boreal Laboratories, thanks David!]