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Amazing Clouds Resembling Stacked Plates Formed Over Mount Washington, New Hampshire, on Sunday. Here’s What They Are
Published: September 16, 2019
Weather observers at the summit of Mount Washington, New Hampshire, photographed a breathtaking sight Sunday as clouds resembling stacked plates or flying saucers formed overhead.
These are called lenticular clouds, which are most common near or downwind of mountain ranges.
(Mount Washington Observatory)
Their flying saucer appearance is owed to the forced ascent of stable air over mountain ranges.
By stable air, we mean air that when forced to rise does not accelerate upward (like how cumulonimbus, or thunderstorm, clouds form) but rather comes back down as it turns colder, or more dense, than the surrounding air.
The lenticular cloud denotes the upward part, or crest, of the mountain wave of air. You can't see the downward part, or trough, of the wave because air moving downward dries out. As long as the ambient weather conditions – such as wind and humidity – are unchanged, the cloud won't move, appearing to hover near the mountain range, as it did near Mount Washington on Sunday.
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