Mesocyclones are convection vortices formed in powerful thunderstorms, which generate many dangerous byproducts. They are most commonly observed in supercell thunderstorms, but they can drive the activity of lesser thunderstorms as well.

A mesocyclone generates many effects as a result of the mixing of warm updrafts, and cold downdrafts. The main effect is hail, which is almost always present if a mesocyclone has formed. The hail generates powerful lightning bolts. Other effects of a mesocyclone include powerful downdrafts, which can take down an aircraft, strong wind shear, and torrential downpour.

The most severe side-effect of the mesocyclone occurs when a downdraft and the flanking line of the mesocyclone collide. The first effects will be a "mammatus", or a bubbly cloud formation. If the downdraft is strong enough, the flanking line will lower and produce a "wall cloud". The final result is the formation of funnel clouds and finally tornadoes.