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film of a tornado emerging from the wall cloud of a supercell in south dakota. a supercell is a severe thunderstorm with a deep rotating updraft. most tornados are associated with supercell thunderstorms, the largest, most severe class of single cell thunderstorms. 

a tornado is created when the cooler downdraft of rear midlevel winds combine with the updraft of warm, moist and horizontally spinning surface level winds, which condense into a funnel as they’re drawn upward into what is called the mesocyclone. (video)