Wind Chill Exposed

Did you know that wind chill is actually a calculation rather than a measurement? The wind chill only affects objects whose temperature cannot drop below the actual air temperature. In other words, increasing heat loss occurs from a person's skin as the wind speed increases and blows the heat generated by the body away. This is why wind chill can be negated by simply covering exposed skin properly. However, wind chill does not account for sky conditions, which can greatly affect how cold a person perceives the air to be.

The National Weather Service implemented a new wind chill chart in 2001 after research concluded that the old chart overestimated the effect of wind chill. The NWS determined the effect more accurately by measuring the temperatures on various parts of a human's face while walking in a chilled wind tunnel with varying wind speeds. The results of the research led to the design of a new wind chill chart and a different mathematical equation designed to calculate it. An example of the change would be a temperature of 20 degrees F and a wind speed of 20 mph using the old chart would yield a wind chill of -10 degrees F. The same temperature and wind speed in the new chart yields a wind chill of 4 degrees. I have included the equations below for those of you interested.

Old Wind Chill T(wc)=.081 x (3.71 x sqrt(V) + 5.81 - 0.25 x V) x (T - 91.4) + 91.4

New Wind Chill T(wc) = 35.74 + 0.6215T - 35.75(V0.16) + 0.4275T(V0.16)

where T(wc) is the Wind Chill in degrees F, V is the Wind Speed in MPH, and T is the temperature in degrees F.

For those of you who may be allergic to decimals or exponents, here is a link to compare the two charts as well minus the mathematics:

http://www.crh.noaa.gov/ddc/?n=windchill

As you can see, the new chart also has a new element. The chart will show you at what combinations of temperatures and wind that frostbite will occur in 15 minutes or less.

While wind chill can be significant in Oklahoma, it tends to have a more extreme impact in the Northern Plains than it does in Oklahoma. Personally I wouldn't be too upset if the wind didn't come sweeping down the plains quite as violently as it normally does this time of year!