Definition
A lens-shaped or almond-shaped cloud that forms at the crest of a standing mountain wave, where moist air is lifted, cools, and condenses on the upwind side and evaporates on the downwind side. Lenticular clouds remain stationary relative to the ground even in strong winds, marking the location of mountain wave activity and often associated with severe turbulence and powerful up- and downdrafts.
Plain English
A smooth, lens-shaped cloud that sits still over or near a mountain, even when the wind is strong. It marks where the air is rising and falling in waves over the terrain.
Context Anchor
Seen in weather reports, preflight planning, and mountain flying when airflow over terrain is important.
Derivation
From the Latin lenticularis, meaning 'shaped like a lentil' — a small, round, lens-shaped seed. The name describes the cloud's smooth, curved, lens-like profile.
Why Pilots Care
Lenticular clouds mark mountain wave activity that can produce severe or extreme turbulence and strong vertical currents.
Analogy
Imagine a cloud shaped like a flying saucer parked right on top of the mountain ridge.
Grounding Statement
Picture a smooth, stacked-disc cloud hanging motionless above a mountain ridge while everything else in the sky is moving — that stillness is the giveaway.
Intuition Check
Do not assume a lenticular cloud is harmless just because it looks smooth and still. It may mark strong moving air and rough conditions around it.
Example Sentence 1
During the preflight weather check, the pilot noticed lenticular clouds forming over the ridge and decided to delay the mountain crossing.
Example Sentence 2
Lenticular clouds over the ridge confirmed the presence of mountain waves, so the flight remained in the valley.