Thread by @harold_hawaiki

🧵What are Altocumulus lenticularis?
What is Lenticular cloud?
Lenticular clouds, technically known as altocumulus standing lenticularis, are stationary lens-shaped clouds that form at high altitudes, normally aligned at right-angles to the wind direction.

When moist, stable air flows over mountains or mountain ranges, a series of large-scale standing waves can develop on the leeward side. Lenticular clouds sometimes form at the top of these waves.

Under certain conditions, long chains of lenticular clouds can form, creating a formation known as a wave cloud.

Flying near lenticular is spectacular, and are to be avoided in light aircraft, or in helicopters, because of the turbulence of the rotor systems that accompany these clouds... Conversely in gliders, we are looking for them actively seek them out.

This is because the systems of atmospheric standing waves that cause "lennies" (as they are sometimes familiarly called) also involve large vertical air movements, and the precise location of the rising air mass is fairly easy to predict from the orientation of the clouds.

"Wave lift" of this kind is often very smooth and strong, and enables gliders to soar to remarkable altitudes and great distances.

The current gliding world records for both distance (over 3,000km) and altitude (14,938m) were set using such lift.

Lenticular clouds have been mistaken for UFOs (or "visual cover" for UFOs) because these clouds have a characteristic lens appearance and smooth saucer-like shape.