Lenticular clouds are a visible sign of mountain waves in the air. However, these waves can be present beyond the clouds, and may exist even when no clouds are formed. On the ground, they can result in very strong gusty winds in one place, with still air only a few hundred metres away.

Where can lenticular clouds be found?

A lenticular cloud is a lens-shaped cloud that normally develops on the downwind side of a mountain or mountain range. This occurs when stable, moist air flows over a mountain, creating a series of oscillating waves.

What is the rarest cloud?

Kelvin Helmholtz Waves are perhaps the rarest cloud formation of all. Rumored to be the inspiration for Van Gogh's masterpiece “Starry Night”, they are incredibly distinctive. They are mainly associated with cirrus, altocumulus, and stratus clouds over 5,000m.