That Wind-Chill Factor

At U.S. bases in the Arctic and Antarctic, the newcomer must quickly learn the 30-30-30 Rule of Survival: when exposed to a 30-m.p.h. wind at --30DEG F., human flesh freezes solid in 30 seconds.

The killing factor is wind chill. The term, glibly cited by TV weathermen but only dimly understood by a flash-frozen populace, is based on a scale that precisely correlates temperature and wind force. Wind chill--expressed in meteorological phraseology as "equivalent temperature"--measures the difference, in impact on exposed skin, between what the thermometer registers and the wind delivers.

The meteorologists' wind-chill table starts at still air (0-m.p.h. wind) and ranges up to winds of 50 m.p.h. While 20DEG on a windless day can be quite tolerable, a 20-m.p.h. wind makes the received effect of that temperature equivalent to -9DEG without wind. The arctic nadir on the scale: at -45DEG, a 50-m.p.h. wind creates the equivalent of -128DEG--a sensation that is not totally unfamiliar to many Americans this year. 30-30-30!

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