Thursday, March 17, 2016

Puffy, Cotton Ball Clouds in the Sky

I was driving back from a weather talk in Westlake Village Thursday afternoon and I couldn't help but notice how beautiful the sky looked.  I've always thought cumulus clouds were fascinating to look at.  Especially when you can watch them grow, and grow, and grow.  And what always amazes me is when the morning starts off cloud free and by the afternoon the sky is filled with puffy, cotton ball looking clouds.

Maybe some of you have even made the observation that on 'fair' weather days the cumulus clouds all seem to have flat bases and all the bases seem to be at the same height.  Ever wonder why that is?

There is water vapor all around us.  You can't see it, but it's there.  When the sun heats up the atmosphere, the air will rise.  As long as the rising air is cooler than the surrounding air it is moving in to, it will continue to rise.  There is a certain point in the atmosphere where the rising air (water vapor) cools and condenses into tiny water droplets  - this is called the Convective Condensation Level (CCL).  This is where the base of the cloud will form, and why cumulus clouds have their flat bases.  From there, the cumulus cloud will continue to grow until it reaches a stable point in the atmosphere.  Once it does, it won't rise anymore.

Cumulonimbus clouds (thunderstorms) can grow to over 40,000ft in height.  Sometimes, these clouds even reach the top of the troposphere if strong enough.  The clouds we had today were no where near that height because there just wasn't that much instability in the atmosphere.

Wednesday afternoon there was slightly higher instability which caused the late afternoon showers, some of which had pea sized hail, to form.  Those did grow taller than the clouds Thursday afternoon.

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