TUESDAY, FEBRUARY 8 - POOR COMPUTER FORECAST OF STORM


The storm that dumped 10" of snow on us two weeks ago was not predicted very well by computer weather models, in part because of problems with the observations that meteorologists feed storm-predicting supercomputers.

Weather balloons provide most of these observations from above the ground. But these balloons are launched just twice a day, and from only about 75 sites across the country.

That's not very many upper-air observations, and as a result, crucial ingredients of a developing storm are sometimes missed. As an example, misplacing the jet stream by just 50 miles in the observations could produce an error of 100 miles in the forecast storm track - and that can mean the difference between just flurries and a foot of snow in your backyard ... or the difference between a foot of snow and an inch of rain.

So computers may be getting bigger and faster, but our ability to get every storm right is still limited by our inability to perfectly observe the atmosphere.

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