A supercell is a thunderstorm that is characterized by the presence of a mesocyclone: a deep, persistently rotating updraft. Of the four classifications of thunderstorms (supercell, squall line, multi-cell, and single-cell), supercells are the least common and have the potential to be the most severe. Supercells are often isolated from other thunderstorms, and can dominate the local climate up to 32 kilometres (20 mi) away.
From a visual standpoint, the video says it all.
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