October 26, 2010

Huge Storm In the Mid-West

There is a huge fall storm in the mid-west. My limited understanding of meteorology is helping my ability to decipher this map, so here we go.   The 1st thing you should notice is all of those tightly packed isobars(maroon circles).  Isobars represent an area of the same barometric pressure.(pressure of the air in the atmosphere).  You can read this a lot like a contour map. The closer those isobars are together, the faster the pressure is changing. In this example, the pressure is dropping QUICKLY as you get closer to the central low, which is in northern Minnesota.  This giant difference in pressure is causing the low to essentially "suck in" all the air from around it. This is why it's such a prolific wind maker. You can see the number "1004" in the middle of Nebraska, that's the barometric pressure there. I know its hard to see, but on each isobar you can see the pressure that it represents. The numbers drop from 1004 all the way down to 970, that's a huge difference in pressure, also known as a "gradient".  The wind they are experiencing is that air being sucked into the low from the surrounding area. A central low pressure of 970 millibars is the equivalent of a Category 3 hurricane. Unbelievable!   The second part of this storm is the cold front that is triggering the thunderstorms across Illinois, Indiana, Missouri and Kentucky.  The counter clockwise motion of this low is sucking cold air from Canada and moving it south and east. The cold air is crashing into the warm air already in place, and lifting it rapidly, causing the thunderstorms(sound  familiar??). The front will be moving east, and will affect us here in the Mid-Atlantic overnight into tomorrow morning.     The low itself isn't moving all that much, so we won't be seeing a lot of this wind, yet at least.

I hope this brief explanation has helped you understand, at least on a high level, why this storm is so strong and such a big deal.  Enjoy!


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