here ya go just a bit of math and your there
Two of the more common formulations for windchill were developed by Siple (1945) and Court (1948). Court modified Siple's formulation only slightly, using "certain observed values" that were apparently ignored by Siple. Both formulations have the same algebraic structure, but with different constants; both provide an equation for heat loss (H) from an exposed surface. Selection of a "baseline" condition of windspeed and temperature allows solving for a windchill temperature at different conditions.
H = ( A + B * sqrt(S) + C * S ) dT
where:
H == Heat Loss, kg cals/m²/hr
dT == temperature difference (°C), between assumed
skin temperature (33°C) and ambient temperature
S == windspeed, m/s
and the constants, A, B, and C are:
Siple Court
A 10.45 9.00
B 10.00 10.90
C -1.00 -1.00
In a practical sense, with the following definitions, use the following formulas for calculating windchill (Siple's and Court's formulas, rearranging terms and substituting for unit conversions):
Twc == windchill temperature
T == ambient temperature
S == windspeed
For °F and mph (baseline conditions of 91.4°F and 4 mph):
Siple: Twc = 91.4 + ( T - 91.4 ) ( .474 + .304 sqrt(S) - .0203 S )
Court: Twc = 91.4 + ( T - 91.4 ) ( .550 + .279 sqrt(S) - .0203 S )
for S >= 4 mph
T < 91.4 °F
Test (Siple): S=20mph, T=20 °F ---> Twc = -10.5 °F
