wind chill

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wind chill,

the cooling effect of wind and temperature combined, expressed in terms of the effect produced by a lower, windless temperature, also called wind chill factor, wind chill temperature, wind chill equivalent temperature, wind chill index, wind chill equivalent index, and wind chill temperature index. Wind chill is based on the rate of heat loss from exposed skin. Under windless conditions air provides an invisible blanket around the skin. As wind speed increases, this layer of heated air is carried away from the body at an accelerated rate, forcing the body either to work harder to generate more heat or cool down. If the actual air temperature is −5°F;(−21°C;) with a 20 mph (32 km/hr) wind, the wind chill temperature is −29°F;(−34°C;). Because wind chill is based the removal of heat from the human body, it does not reflect the increased rate of heat loss for inanimate objects such as automobile radiators under the same conditions but they also experience a faster heat loss with increasing winds.

The term wind chill was coined by the American geographer Paul A. Siple in his dissertation, Adaptation of the Explorer to the Climate of Antarctica, (1939). Subsequently, on the third Byrd Antarctic expedition, Siple and American geologist Charles Passel determined how quickly extreme conditions could produce frostbite on exposed skin. By 1945, Siple and Passel had published a set of numbers expressing heat loss as a function of temperature and wind speed.

A wind chill advisory is issued when the forecast projects a wind velocity of at least 10 mph (16 km/hr) producing a wind chill temperature of −15°F; or lower for 3 hours or more. At these values wind chill is more of a nuisance than it is life threatening. A wind chill warning is issued when the forecasted wind chill temperature is −25°F; or lower, which can be life threatening if the individual is not suitably dressed. Persons who go outside under such conditions may experience frostbite and other cold-related symptoms in a matter of minutes, even if properly clothed for normal winter conditions, and longer exposures may prove fatal.

wind chill

[′win ‚chil]
(meteorology)
That part of the total cooling of a body caused by air motion.
References in periodicals archive ?
Vertical International, based in Ruthin, Denbighshire, has designed a thermometer device which takes account of the wind-chill factor and is small enough to be fixed to equipment such as skis or ice axes.
The 57-year-old will wear a spacesuit to allow him to breathe and protect him from the extremely low temperatures, which can drop as low as -90C plus wind-chill factor.
Scotland's Louise Scott and American Tom Ferrel provide the biggest threat to the Scandinavian over a course where temperatures can fall to the equivalent of -50infinityC with the wind-chill factor.
Clerk of the course Andrew Tulloch said: "Last night was one of the coldest we've had and with the wind-chill factor it's just not coming out of the ground.
Lips: Beautiful colour combined with moisturising benefits are a must when the wind-chill factor kicks in.
The big chill will arrive towards the middle of the week when temperatures could plummet as low as minus 8C, although forecasters warn the wind-chill factor will make it feel even colder, possibly as low as minus 14C.
Yesterday's single-digit high of 9 and overnight low of zero, with a wind-chill factor of 10 to 15 below, enveloped the area in a blustery blanket of frigid air.
On the worst days, Pete has encountered temperatures with a wind-chill factor of -32C and snow drifts two metres deep.
Day time temperatures are expected to drop as low as 1C (34F), with the wind-chill factor making it feel even colder.
But, being driven by a developing anticyclonic ridge, the wind direction backed from souithwesterly round to southeasterly overnight and to east by midday, when the Sun's warmth returned and the wind-chill factor became less oppressive.
There could also be coverings of several inches of snow in lower-lying parts of the region and it will feel bitterly cold throughout the weekend with a significant wind-chill factor, according to the Met Office.
A secret Met Office report leaked to the Mail urged that the wind-chill factor in Scotland should be taken into account when the extra pounds 8.50 payments are triggered.