Lenticularis clouds are lens-shaped clouds, with a smooth layered appearance. Lenticularis often shows iridescence if it is near or in front of the sun. Beautiful lenticularis forms over and downwind of mountain ridges whenever there are strong upper-level winds, such as the jetstream. Mountain lenticularis are stationary and mark the crests of invisible gravity waves in the air flowing over the mountain. The sometimes flying-saucer-like appearance of lenticularis undoubtedly accounts for several fake UFO reports.

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