A diagram of a supercell in the Northern Hemisphere, showing the different parts of its structure. Supercells are thunderstorms characterized by the presence of a mesocyclone: a deep, persistently rotating updraft. Of the four types 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 weather up to 30 kilometres (20 mi) away.Diagram: Kelvin Ma