Storm types#storm#rotation

Supercell

At a glance

A long-lived, rotating thunderstorm. The mesocyclone at its core lets it persist for hours, produce giant hail, and — under the right conditions — drop tornadoes.

Deep dive

Supercells are defined by the presence of a persistent, deep mesocyclone — a rotating updraft. They require moderate-to-strong deep-layer shear (~20+ m/s over 0–6 km) and sufficient CAPE to sustain a deep updraft.

Classic / classic-HP / LP subtypes differ by precipitation efficiency and structure:

Classic — balanced inflow/outflow, visible vault, tornadoes common.
HP (High Precipitation) — rain-wrapped mesocyclone, dangerous to chasers because tornadoes are often invisible; UK supercells often trend HP.
LP (Low Precipitation) — dry skeleton of a supercell; rare in UK.

UK supercell days are rare (~0–5 per year) and almost always set up ahead of a surface low with Spanish Plume moisture.