Wind Chill!!!

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Background
How cold is it outside? Simply knowing the temperature doesn't tell you enough about the conditions to enable you to dress sensibly for all winter weather. Other factors including wind speed, relative humidity and sunshine play important roles in determining how cold you feel outside. A description of the character of weather known as "coldness" was proposed about 1940 by scientists working in the Antarctic. The "wind chill index" as developed to describe the relative discomfort/danger resulting from the combination of wind and temperature.

The wind chill index describes an equivalent temperature at which the heat loss from exposed flesh would be the same if the wind were near calm. For example, a wind chill index of -5 indicates that the affects of wind and temperature on exposed flesh are the same as if the air temperature were 5 degrees below zero even though the actual temperature is much higher.

The importance of the wind chill index is as an indicator of how to dress properly for winter weather. (Wind chill does not affect your car's antifreeze protection, freezing of water pipes, etc.) In dressing for cold weather an important factor to remember is that entrapped insulating air warmed by body heat is the best protection against the cold. Consequently, wear loose-fitting, lightweight, warm clothing in several layers. Outer garments should be tightly- woven, water-repellant and hooded. Mittens snug at the wrist are better protection than fingered gloves.

The formula the National Weather Service uses to compute wind chill is:

T(wc) = 0.0817(3.71V**0.5 + 5.81 -0.25V)(T - 91.4) + 91.4 T(wc) is the wind chill V is in the wind speed in statute miles per hour T is the temperature in degrees Fahrenheit

The formula to calculate a Celsius wind chill using V as the wind speed in kilometers per hour and T in degrees Celsius is: T(wc) = 0.045(5.27V**0.5 + 10.45 - 0.28V) (T - 33) + 33

Excerpted from: Weather, Road Conditions, and Travel Advisories, http://www.cvfn.org/weather/windchill.html, 26 December, 1997

Gene's Measurements and Weather Page: Wind chill Factors: A much overused and misused measurement, http://ourworld.compuserve.com/homepages/Gene_Nygaard/windchil.htm, 26 December,1997.

Resources and Reference Materials
For a neat, interactive program that calculates temperature based on wind chill, go to:http://leav-www.army.mil/weather/Windchil.htm

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