Wednesday, January 6, 2010

Too Cold to Snow?

'fraid not.  Right now it is snowing lightly with 1 mile visibility at Dickinson, ND with a temperature of 0°F, and snowing moderately (1/2 mi. visibility) at Hastings, NE with a temperature of 10°.  Winds are gusting to nearly 50mph in much of western Nebraska and South Dakota.

Speaking of cold, I was asked to compare this cold air outbreak to the one in 1990 and 1983. There is one major change since then you may want to be aware of:  The wind chill index was redefined in 2001.  While there were good scientific reasons to do so, the wind chills will seem less impressive during this cold wave than those historic periods of cold.

Some examples......
If the temperature is Zero and the wind 30mph, the "old wind chill" was -48° and the new -26
If the temperature is -10 and the wind 35mph, the old wind chill was -66 and the new "only" -41

I was in Kansas City during the Great Coldwave of 1983 and I can say I experienced wind chills of nearly -70°F.  Today, the way the new wind chill is defined, that would be nearly impossible.

So, when an old timer says, "I remember when wind chills were seventy below," they will be speaking the truth.  But, if the wind chill at the moment happens to be -43, it is just as cold was it was in "the good (bad?) old days."

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