IEM Daily Feature
Friday, 18 July 2003

What is this CAP?

Posted: 18 Jul 2003 07:09 AM


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CAP illustrated in 00z Davenport sounding on 18 Jul 2003.
Your favorite Meteorologist has probably been using the word CAP recently to desribe why their forecast of rain did not pan out. A CAP is simply a layer of warmer air that impedes rising motions from below it. Either the air below needs to be warmer than the CAP (breaking thru the CAP) or needs sufficient momentum to overcome the CAP. The CAP can also be weakened by other processes thus allowing upward motion.