These lens-shaped clouds typically form where stable moist air flows over a mountain or a range of mountains. When this happens, a series of large-scale standing waves may form on the mountain’s downwind side. If the temperature at the crest of the wave drops to the dew point, moisture in the air may condense to form lenticular clouds. As the moist air moves back down into the trough of the wave, the cloud may evaporate back into vapor. So lenticular can appear and disappear relatively quickly. Plus they’re not familiar to people who live in low-lying or flat terrain. And, just to confound things, lenticular clouds have also been known to form in non-mountainous places, as the result of shear winds created by a front. For all of these reasons, lenticular clouds are often mistaken for UFOs (or “visual cover” for UFOs). Enjoy the photos! Thank you to all who posted.
Bottom line: Photos and video of lenticular clouds in various parts of the world, from EarthSky’s community on Facebook and G+.