Lenticular Cloud

A smooth, lens-shaped cloud often mistaken for a UFO/Weather & Climate

Lenticular clouds (altocumulus lenticularis) are smooth, lens-shaped or saucer-shaped clouds that form when stable, moist air flows over a mountain or ridge and creates standing waves on the downwind side. Unlike most clouds that move with the wind, lenticular clouds remain stationary, hovering in place as air continuously flows through them. Their smooth, rounded shape and stationary behavior have led to many UFO reports. They can stack in layers, forming dramatic 'pile of plates' formations. Pilots avoid them because the turbulent rotor zones beneath can produce severe downdrafts. They are commonly seen near mountain ranges worldwide.