A thunderstorm characterized by persistent, mesoscale rotating updraft (referred to as mesocyclones) that are deep relative to the cumulonimbus cloud top (usually 8 to 15 kilometers). Lasting as long as 6 hours, supercells may produce every type of hazardous weather: large damaging hail, frequent cloud-to-ground lightning, flash flooding, damaging outflow winds, and tornadoes. Most strong or violent tornadoes are spawned by supercells. The supercell updraft remains horizontally displaced from the downdraft so that the storm is typically longer lived than the air-mass thunderstorm. Supercells form in environments with large vertical wind shear and high instability.
A thunderstorm with a persistent rotating
updraft . Supercells are rare, but are responsible for a remarkably high percentage of severe weather events - especially
tornadoes , extremely large hail and damaging
straight-line winds . They frequently travel to the right of the main environmental winds (i.e., they are
right movers ). Radar characteristics often (but not always) include a
hook or
pendant , bounded weak echo region (
BWER ),
V-notch ,
mesocyclone , and sometimes a
TVS . Visual characteristics often include a
rain-free base (with or without a
wall cloud ),
tail cloud ,
flanking line ,
overshooting top , and
back-sheared anvil , all of which normally are observed in or near the right rear or southwest part of the storm (see picture)
Storms exhibiting these characteristics often are called classic supercells; however
HP storms 
and
LP storms 
also are supercell varieties.
