Mesocyclone

A mesocyclone is a vortex of air within a convective storm. It is air that rises and rotates around a vertical axis, usually in the same direction as low pressure systems in a given hemisphere. They are most often cyclonic, that is, associated with a localized low-pressure region within a severe thunderstorm. Such thunderstorms can feature strong surface winds and severe hail. Mesocyclones often occur together with updrafts in supercells, within which tornadoes may form at the interchange with certain downdrafts.