How do clouds form?
Mountains also cause air to rise. As the wind blows across a mountain range, air rises and cools and clouds can form on the windward side. This is why windward sides of mountain ranges tend to get heavy precipitation.
When the air sinks on the leeward side of the mountain range, it is usually much drier and warmer than it was to begin with. (To learn more, see this lapse rate page.)
Despite being drier, lenticular clouds can form on the leeward side of the mountain. These form because the air moving over the mountains has been disturbed, and can continue to flow in a wave-like pattern for hundreds of kilometers downwind of the mountains. Each time air rises in the waves, water vapor condenses and a cloud forms. These clouds are sometimes mistaken for flying saucers. Can you see the resemblance in these pictures?
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