JUST IN TIME FOR WINTER, NATION GETS NEW WIND CHILL INDEX FORMULA
August 17, 2001 As most of the
nation copes with simmering summer heat, NOAA's
National Weather Service this week was preparing for winter.
Starting with the 2001-02 winter, forecasters will use a new
Wind Chill Temperature Index, designed to calculate a more accurate
reading of how the cold air feels on the human skin. (Click
image for larger view.) [NOAA Photo: The Potomac River
in Sandy Hook, Maryland.]
Since 1945, the United States and Canada have used an index, which relied on observed winds 33 feet above the ground, and focused on how fast the cold temperaturescombined with windsmade water freeze. The new index accounts for the wind effects at face level, and a better calculation for body heat loss. For example, under the old index system, an air temperature of 20 degrees, with a 15 mph wind, translated into a reading of five degrees below zero. The new index calculation would translate the same conditions to six degrees above zero.
"Exposure to cold, biting air for long periods of time is dangerous," said retired General Jack Kelly, director NOAA's National Weather Service. "Our main goal was to use modern science in revising the index so that it's more accurate and makes the human impact more prominent."
The new index will be based on:
For the past year, the National
Weather Service, acting on behalf of the U.S.
Office of the Federal Coordinator for Meteorological Services
and Supporting Research, has led a team of international
scientists with the goal of creating an international standard
wind chill index among the meteorological community. Last spring,
the scientists conducted clinical trials and the results helped
to verify and improve the accuracy of the new formula.