Supercell

A long-lived thunderstorm with a deep, rotating updraft called a mesocyclone. Its organized rotation can produce large hail, damaging winds, and tornadoes.

Mesocyclone: A deep, rotating updraft within a thunderstorm, typically several kilometers wide. This organized rotation defines a supercell and helps separate it from ordinary thunderstorms.
Atmospheric instability: A state in which displaced air can accelerate vertically because of buoyancy. Instability supplies the buoyant energy that drives a supercell’s strong updraft.
Doppler weather radar: Radar that uses frequency shifts in returned signals to estimate motion toward or away from the radar. Velocity data can reveal the rotation associated with a supercell’s mesocyclone.
Classic supercell: A supercell with a distinct updraft, downdraft, and precipitation structure, often including a rain-free base. It is the textbook structural form of a supercell.
Ordinary cell thunderstorm: A short-lived thunderstorm with a single updraft and downdraft that usually evolve together. Its brief, nonrotating structure contrasts with a supercell’s persistent mesocyclone.
Wind shear: A change in wind speed or direction across distance or altitude. Vertical wind shear helps create the storm rotation that a supercell organizes.
Convective available potential energy: The positive buoyant energy available to an air parcel rising through the atmosphere. CAPE quantifies the energy that can support vigorous supercell updrafts.
Severe Thunderstorm Warning: An official alert that a severe thunderstorm is occurring or imminent in a specified area. Warnings communicate threats such as supercell-produced destructive winds and large hail.
High-precipitation supercell: A supercell whose heavy precipitation wraps around or obscures its rotating updraft. Its rain-wrapped structure can conceal dangerous rotation and tornadoes.
Squall line: A line of thunderstorms that can extend for hundreds of kilometers along or ahead of a front. Squall lines organize storms into a line, rather than around one dominant rotating updraft.

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