It's the second half of August; summer is slipping away, so it's time to talk wind chill. "No, it's NOT!" you say. And I don't blame you. There are still plenty of warm days ahead before the first flakes fly. But come this winter, a new "Wind Chill Temperature" (WCT) will be used and it may actually warm your heart … or at least your skin a little bit.
The old standby WCT was computed by using an empirical mathematical formula based on field experiments in the Antarctic. The cooling rate of various containers of water was measured under varying wind and temperature conditions. Once the formula was devised and the wind chill chart put together, all we had to do was match the current air temperature with the current wind speed and we would get the "feels like" temperature. At least that's what we were told. But there are a lot of problems with this method.
The human skin and body does not cool like a container of water. The wind speed used to calculate the WCT is based on an anemometer height of 33 feet, the standard height for wind speed measuring equipment used by the National Weather Service. Most humans measure a height of about five and a half to six feet tall. Thirty-three feet is a bit too tall. Typically the wind speed at that height is faster than the speed at our level. And finally, the WCT was never meant to be the "feels like" temperature since every person feels a little different under the same chilly, windy conditions. It was meant to measure the cooling rate of the body. The lower the value of the WCT, the more quickly our bodies will lose heat.
The new WCT is a product of several agencies and organizations, including the National Weather Service, Meteorological Services of Canada, Indiana University-Purdue University in Indianapolis, the University of Delaware, the University of Missouri and the International Society of Biometeorology.
The result contains the following improvements to the WCT equation:
- Use wind speed calculated at the average height (5 feet) of the human body's face
- Base the calculations of heat loss on a model of the human face
- Incorporate modern heat transfer theory (heat loss from the body to its surroundings during cold and windy days)
- Use a consistent standard for skin tissue resistance.
For example, assuming an air temperature of 5 degrees above zero and a wind of 30 miles per hour, the old WCT = -41 degrees, the new WCT = -18 degrees. Yes, it will be a warmer WCT and a more realistic one.
As always, whenever the WCT gets below zero, take extra precautions to make sure you are dressed appropriately. Dress in layers and try to cover as much exposed skin as possible. WCT is NOT a "feels like" temperature, but an indication of how quickly your body will cool if not properly clothed. Frostbite occurs in 15 minutes or less at WCT values of —18 or lower.
All right, get those calculators out. Here is the new and improved WCT formula:
Wind Chill (in degrees Fahrenheit) = 35.74 + 0.6215T — 35.75(V0.16) + 0.4275T(V0.16)
Where (V0.16) refers to the wind speed value in miles per hour raised to the power of 0.16, and T is the temperature in degrees Fahrenheit.
Watch Vince Condella on Fox 6 Sunday through Thursday at 5, 6, 9 and 10 p.m. You can see the FOX 6 weather forecast around the clock at www.fox6milwaukee.com
