An almond-shaped cloud that appears stationary but may contain winds of 50 knots or more is called what?

• A. Lenticular cloud
• B. Cumulus cloud
• C. Cirrostratus
• D. Altocumulus

Answer: (A)

Lenticular clouds form when stable air flows over mountain terrain and creates standing waves on the lee side. Moisture condenses at the crests of these waves, producing smooth, almond- or lens-shaped clouds. They often look stationary because the wave pattern is fixed relative to the terrain, even though the air inside the wave can be moving rapidly. In the rotor region beneath or around the cloud, winds can be very strong—50 knots or more—making them a warning sign of potentially severe turbulence for gliders. The other cloud types don’t share this lens shape or the stationary appearance: cumulus clouds are puffy and evolving, cirrostratus are thin high-altitude veils, and altocumulus are mid-level patches or waves, not the distinct lenticular form.