Wind Chill and Hot Air
Wednesday, January 30, 2019
It’s cold out there, but fortunately the weather forecasters are warming us with hot air.
In the midst of the chill known as a polar vortex dipping deep into the center of the country, it’s hard to know what the temperature is because the weather reporters deliver it in “wind chill.” They don’t just give the temperature. They tell us it’s going to “feel” like zero or, in Chicago, it could be 60 below with the wind chill.
The anchor of the “CBS Evening News” said, “Here is a look tonight at the ‘feels like’ temperatures for tomorrow morning,” then showed an array of temperatures from minus 25 to 59 below zero. He threw to a reporter who said it was colder in the Dakotas than the top of Mr. Everest.
One of the worst things that ever happened to weather reporting is the discovery of the wind chill. Ten degrees isn’t dramatic enough when they can report it as five below with the wind chill. Pretty soon they’ll be telling you the temperature in terms of long-underwear alerts and liquor store advisories.
What wind does when it’s cold is reduce the time it takes to cool an object, or a person. The wind chill index is based upon the effect of wind and cold air on a naked human body. The body in 40 degree air with a 10 mph wind would lose heat at the same rate as if it were 28 degrees outside.
The wind chill index is a descending scale. The colder the air and faster the wind, the chillier the chill. According to the index, when the air is 25 degrees and the wind is blowing at 10 mph, it feels like 10 degrees. At 30 mph, it’s minus 10, or anyway, it supposedly “feels” like 10 below.
There’s no doubt that wind makes cold air more bitter. You get frostbite faster. But can the wind chill freeze a glass of water when the air temperature is above freezing? No, it can’t. If the air is 35 degrees and the wind is blowing at 20, the wind chill “feels” like 11 degrees, but that glass of water won’t freeze. The wind can’t chill an object below the actual air temperature.
When the wind chill index makes the weather look apocalyptic, your thermometer is telling you the actual temperature. So, is it colder in the Dakotas than the top of Mt. Everest? No, it isn’t. In January the actual air temperature on Mt. Everest averages minus 36 and can plunge to 60 below. Most days the wind blows up to 100 mph. If you still want to know what that is in wind chill, at 25 below with a 40 mph wind it’s 95 degrees below zero. And, interestingly, beyond 40 mph, the wind chill has no further effect.
Of course, no one goes to the top of Mt. Everest or walks down Michigan Avenue in Chicago naked. They wear clothes that defeat the temperature and wind chill. So here is a plea to the weather forecasters and television anchors: just tell us the temperature and we’ll decide how it feels.
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