A thunderstorm with a persistent rotating updraft. It produces most violent tornadoes, very large hail and damaging winds, and it can last for hours.
Supercell cross-section. Warm, moist air flows in low on the right and rises in the rotating updraft; the wall cloud and tornado form under it, between the rain-and-hail core and the rear-flank downdraft.
How to spot it
Look for a tall, tiered tower with a flat anvil, a smooth rotating base, and a clear boundary between the warm inflow side and the rainy side.
On radar
A large, isolated echo with a hook or a V-notch, a tight area of strongest reflectivity, and a bounded weak echo region where the updraft is.
Safety
Supercells can produce giant hail and sudden tornadoes. Keep distance and an escape route, and never chase into the core.
