The other day, leaving my house, I thought how delightfully comfortable I felt. It was only about 30 degrees and somewhat overcast, but eerily still. There were the typical remnants of the previous day's storm - white snow growing brown around the edges, some ice patches, and gritty looking automobiles. But mostly, it felt much warmer than the reported 30 degrees.
This got me rethinking the "wind-chill factor," that weathercasters' version of a screaming tabloid headline, calculated to make your jaw drop. We all know how the windchill works: You start with a temperature reading and adjust it downward for wind velocity.
Wind-chill index charts depict the extent to which wind makes us feel colder. For example, we might be told that the temperature is 30 degrees, but with a wind velocity of 15 m.p.h., it feels like 9 degrees.
But there's a problem with that. That it feels like 9 degrees is based on the assumption we're accustomed to temperatures accompanied by absolutely no measurable wind. But how common is a windless day - particularly in the Northeast or Midwest? Not very.
For instance, the average wind velocity that I randomly tracked for the Boston area in the past month was about 15 m.p.h. That means on an average day, we expect to feel wind and the comfort - or discomfort - associated with an average wind velocity accompanying a given temperature. So in truth, what 30 degrees really feels like to most of us, most of the time, is 30 degrees with 15 m.p.h. winds. That's how we think about 30 degrees.
But there is no symmetry in this. If we must deduct degrees from the actual temperature to know what it really feels like, we should start with the average wind velocity. This means that if the temperature is 30 and the wind velocity is the average 15 m.p.h., then there should be no adjustment at all. Basically, what 30 degrees feels like to us is 30 degrees with some wind. So, "wind chill" should only be invoked when wind velocity is higher than average.
And here, more importantly, is where the need for symmetry enters: What happens when the wind is less than average?
When there is calm, hikers, runners, public-transit users, and cross-country skiers will usually say, "Gosh, it doesn't feel like 30 degrees today, it feels much warmer." So when the wind is less than average, we should have a "calm-adjustment factor." That is, with 30 degrees and no wind, it probably feels more like 40 degrees.
The way it works now, we only get bad news. Just as we awaken, our homes too cold for us to get out of bed and go turn up our thermostats, we hear, "The temperature is 'x,' but it feels much colder."
Well, the truth is, sometimes it feels much warmer than "x"!
During these short days of winter, we deserve a break now and then, some inspiring news once in a while. Would it really hurt anyone if our weather forecasters could one day report, "It's 20 degrees this morning, but with no wind it really feels like 32. So get out there and enjoy the calm-adjustment factor."
*Robert A. Rosenthal is a professor of economics at Stonehill College in Easton, Mass.
(c) Copyright 2000. The Christian Science Publishing Society