Caption:
Dangerous mesocyclone of a supercell thunderstorm that produced softball-sized hail near Altus, Oklahoma during the evening of April 18, 1992. Mesocylones are most commonly observed in supercell thunderstorms with a mix of warm updrafts and cold downdrafts, often producing hail. Supercells or rotating thunderstorms usually have a flared or bell-shaped cloud base and are sometimes associated with tornadoes. They occur commonly in the Great Plain states with a counter-clockwise rotation.