Why aren't lenticular clouds moved by the wind?

Question

My book tells me that altocumulus lenticularis are not moved by wind but rather the air just flows through them without effect on their position. How come they are the only cloud type that is stationary?

Answer 1

Clouds form when particular conditions of temperature and humidity intersect.

In the case of lenticular clouds, those conditions occur at specific locations slightly downwind from the tops of mountains -- a standing wave forms in the air between areas of low and high humidity, much as standing waves form in river rapids.

Source: National Park Service

The standing waves can only form when wind is blowing over the mountain, and so the region of air where the standing waves create the conditions to form clouds is pinned down by the mountain.

The region doesn't move, but the air and water molecules do.

• New moist air blows over the mountain, following the standing wave, and into a zone of lower temperature, where it condenses into the droplets that form the cloud.

• Still following the wave, the droplets blow into an area of higher temperature and evaporate again.

Source: National Weather Service

Also, the standing waves that guide moist air to form lenticular clouds are an example of laminar flow.

Other clouds appear to move because and the air where they form is moving turbulently, and they are also not controlled by temperature (they move within a layer about the same temperature), only moisture.