Friday, September 24, 2010

Why so windy?

The image on the left is a surface plot from 8am this morning.  On it you'll find temperature contours, the yellow dashed lines, and isobars outlined in the cyan color.  Isobars are a meaure of constant pressure.  Wind is caused by changes in pressure and the closer the isobars are to each other, the stronger the wind will be.  A fairly strong area of low pressure sits just north of Wisconsin and as it continues to deepen winds will gust through the Great Lakes.  Not only do we look at the surface, but we also look above us to see what's going on.  As Eric Nefstead mentioned last night, winds a couple thousand feet up are screaming in around 70-75 mph, and even higher.  Sometimes we can actually tap into those types of wind speeds aloft and bring them down to the surface through a process called mixing.  Obviously we won't see winds of 70 mph, but winds could gust near 40 mph before calming some later this evening.

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