Tuesday, July 7, 2020
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Reports of 100-below wind chills on Mt Washington

Students at Our Lady of Good Counsel High School in Olney, Maryland, had their first snow day this year on Thursday, according to a report in The Talon student newspaper, but the “bomb cyclone,” as it has been dubbed, in a day when every name has shock value, made conditions much worse in New England.


Mount Washington (Aneese/iStock)

A bomb cyclone is actually a thing, but of the 40 or 50 that happen every year, most of them stay out over the ocean and nobody really notices—unless you’re a weather geek. The problem with this one, which came ashore last week and brought snow drifts six feet high to Maryland’s Eastern Shore and worse conditions in Boston, was the cold air it brought with it.

Wind chills on Mount Washington in New Hampshire were reported as being –100°F. That gives me an opportunity to learn a little about wind chill. How bad is that temperature? What is the danger?

In Canada, where the Northwest Territory tundra experiences colder wind chills than we in the US can probably imagine, meteorologists report wind chill using the units of watts per square meter. It refers to the heat that is lost by one square meter (of exposed skin), and for convenience sake, they have tables that show the temperature “equivalents.”

This is a much more scientifically accurate way to report wind chill, since degrees Fahrenheit (or Celsius) refers to the air temperature, the amount of “heat” in the air. Any molecule that’s above absolute zero has some “heat” since that’s just the energy of the molecules. Wind chill isn’t measuring the heat of the molecules blown around by the wind but rather the amount of heat lost by exposed skin because of the wind’s cooling effects.

For example, if the temperature is 40°F but the wind chill is reported as 15°F, how long will it take water puddles to ice over and make the roads slippery? The answer is never. There’s still 40°F of heat in the air molecules, but if you’re walking around in a bathing suit, your skin might freeze because the wind cools it down by taking the “heat” away from it.

That “loss” of heat is more accurately reported in units of power, not temperature, but since even the Canadians publish equivalency tables, I can go with it. What it means, though, is not that there’s no global warming, as some politicians may claim (see the January 5 episode here), but that the wind is more violent than it has been in the past and produces conditions that could freeze exposed skin very fast, provided there’s no heat energy being generated by your body to replenish some of the heat energy lost to the wind as you walk outside.

Paul Katula is the executive editor of the Voxitatis Research Foundation, which publishes this blog. For more information, see the About page.

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