Ever wondered how we go from still air to swirling storm? In this video meteorologist -- and storm chaser! -- James Spann explains where tornadoes come from.
In truth, we don't know for certain -- the exact same conditions won't necessarily give rise to a tornado every time. But we have learned a lot from observations made by scientists over the years. This video really neatly summarises what happens in just four minutes. And this guy really knows; he's driven into the things. [TED Ed]