What are those circular clouds above Mount Rainier?

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by Jeff Renner

Bio | Email | Follow: @Jeffrennerwx

KING5.com

Posted on April 22, 2009 at 6:58 PM

Updated Thursday, Jan 14 at 9:20 AM

What are those circular clouds that appear above Mount Rainier at times?

Those "round" clouds are called "cap" or "lenticular" clouds. They typically form over the taller mountain peaks, such as our volcanoes, as moist air is lifted high enough to cool and condense water vapor into liquid water droplets which produce clouds. The process is similar to what allows you to "see your breath" when you breathe out on a cold day. As the wind moves over and down the backside of a mountain peak, it sinks, warms and evaporates the moisture. Although it looks as though the cloud is "stationary", it's actually being continuously created on the upwind side, and dissipating on the downwind side. Such clouds are a good "early indicator" of approaching weather.

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