Hi Tim,
It appears as if DA 3.10a is still using the pre 2001 wind chill formula when calculating wind chills. Below is a graphic.
For the site circled in red in South Dakota (KD07), the temperature in Fahrenheit is plotted as -4 (-20.0C in the QC window) and the wind is from the north at 18 kts. DA plots the wind chill in Fahrenheit as -45 (lower right number on the plot for D07). The NWS webpage on the left has the wind chill calculator using the formula in use since 2001. Plugging in the -20.0C temp and 18 kt wind, gives a wind chill in Fahrenheit of -27.6.
Could this be fixed, or an additional Wind Chill value added for the newer formula? Thanks.
George
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Effective April 12, 2021, we had to delete about 8000 frivolous spammer accounts going back over a year. There was no way for us to locate all legitimate user applications, so some may have been deleted. If you are an actual user who created an account since March 2020 but did not get approved, please register again. You can also contact us via the Contact link on the main Weather Graphics webpage to get assistance. When you contact us, it is essential you provide brief but detailed info on your meteorological background or inform us of any previous order you've made, this way we can tell you are a legit user, otherwise we will assume it is a spammer trying to bypass the application checks. Thanks. -Tim
Digital Atmosphere using pre-2001 Wind Chill Formula
Digital Atmosphere using pre-2001 Wind Chill Formula
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Tim Vasquez
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- Posts: 529
- Joined: Sat Nov 22, 2003 10:47 pm
Re: Digital Atmosphere using pre-2001 Wind Chill Formula
Looking around at the current formulas, it does look like we need to update it.
Here is the formula we have been using so far. I will make some changes to add the new index and allow access to the old formula for those that want to use it.
_____________________________________________
function windchill(tempc:real;windspd:real):real;
var
ftemp, workvalue : real;
begin
ftemp := ctof(tempc);
if (windspd < 4) then windspd := 4;
workvalue := ((((33 - (10.45 + (10 * sqrt (windspd /
1.943)) - (windspd / 1.943)) * (33 - ((ftemp - 32)
* 0.5556)) / 22.04) / 0.5556) + 32));
result := workvalue;
end;
Here is the formula we have been using so far. I will make some changes to add the new index and allow access to the old formula for those that want to use it.
_____________________________________________
function windchill(tempc:real;windspd:real):real;
var
ftemp, workvalue : real;
begin
ftemp := ctof(tempc);
if (windspd < 4) then windspd := 4;
workvalue := ((((33 - (10.45 + (10 * sqrt (windspd /
1.943)) - (windspd / 1.943)) * (33 - ((ftemp - 32)
* 0.5556)) / 22.04) / 0.5556) + 32));
result := workvalue;
end;