Persistent stable clouds form in the Sierra Wave.
Winds form standing waves over the mountains here, just as flowing water does over rocks. Dubbed the “Sierra Wave”, these formations give themselves away with pressure changes, which condense moisture into clouds. These clouds are often “lenticular”, meaning they are shaped like lenses. I suppose a physicist might say the bending of the air is in fact a lensing effect. Water isn’t compressible, so we don’t see a similar effect in streams.
The curious thing about lenticular clouds is that they don’t float by. Cumulonimbus floating over the plains move with the currents, so the sky is ever changing. Lenticular clouds change shape slowly over time, but are mostly stationary, an integral part of their environment. The formation in this photo lasted for several hours.
Our lenticular clouds are often layered, like fine pastry, but I don’t know why. I do know that the edges catch light and add contrast to photographs, so the clouds don’t just appear as blobs. Lenticulars are also very smooth, not bumpy like cumulonimbus, nor wispy like cirrus. This makes them a real puzzle for autofocus algorithms. Often I will look at a shot in post-production and think it out of focus, only to look down at the mountains and see they are sharp and crisp.
Lenticular clouds are fascinating to watch because I like to think about the physics of their creation, but since they have a very defined and stable form, they don’t lend themselves to the cloud shape game.