Lenticular clouds

A stunning series of lenticular clouds, near the northwestern edge of the Penny Ice Cap.  Lenticulars are formed when strong winds blow across complex terrain, causing the water vapor in the air mass to alternately compress, then decompress, and thus condense into shapes which roughly mirror the terrain beneath.  They are also near-certain indicators of turbulence.

Credits: 
NASA/John Sonntag
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