Maybe you can try to use the Australian model for “Apparent temperature”, which also integrates humidity, but uses only operations that we have available in Facers tools set.
It produces slightly different results at some extremes like complete calm but, maybe it is worth a try. It also should work with different temperature array than the Wind chill, which is meant to work best with temperatures close to and below freezing point. You can compare results of the “Wind chill index” by inserting same test values into both calculators.
5 Likes
Hi all
For one, it only makes sense to talk about a chill factor when you have 10°C or less. So that may be a condition you want to consider.
There is an easier formula which is good enough. It is based on a few assumptions, such as being at sea level and humidity is not factored in either.
Formula for Celsius and speed as Kmh:
wind chill = 13.12 + (0.6215 * T) – (11.37 * v * 0.16) + (0.3965 * T * v * 0.16)
Facer Wind speed is in m/s, multiplying that with 3.6 gives you kmh.
4 Likes
I looked at this first but couldn’t find a humidity weather tag in Facer either.
2 Likes
Unfortunately I also looked at this one and they forgot to superscript:
-
W = 13.12 + 0.6215 * T – 11.37 * v 0.16 + 0.3965 * T * v0.16
v0.16 should have the 0.16 as superscript and read as v^0.16 not v*0.16
3 Likes
Ah! OK, thanks. Probably the “back tick” missing on that page when quoting formulas…
4 Likes
#WCHN# Current Humidity Number
4 Likes
Cooking with gas:
Haven’t quite worked it out yet. Been a bit distracted again with unneeded but understandably neccessary post councilling and so on but I have the brackets wrong myself so have a consistant but wrong answer for feels like using the previous: https://www.meteoswiss.admin.ch/weather/weather-and-climate-from-a-to-z/wind-chill.html
1 Like
will look at that anew tomorrow. Nit sure why I could not see it in the tag list. Cheers
3 Likes
this works for apparent temperature in metric units (round(#WCT#+0.33*#WCHN#/100*6.105*exp(17.27*#WCT#/(237.7+#WCT#))-0.7*#WND#-4)) or
(round(#WCT#+0.0201465*#WCHN#*exp(17.27*#WCT#/(237.7+#WCT#))-0.7*#WND#-4))
And this one seems to work for imperial units setting
(round((((#WCT#-32)*5/9)+0.0201465*#WCHN#*exp(17.27*((#WCT#-32)*5/9)/(237.7+((#WCT#-32)*5/9)))-0.7*#WND#*1.6/3.6-4)*9/5)+32)
4 Likes
@petruuccios Thanks - it works perfectly!
My only problem is how you got to the above from the original formula - could you please give me the original formula so that I can try and see how you got from one to the other?
Thanks again.
2 Likes
It comes from the calculator page I suggested earlier, it is also on wikipedia.
I just substituted the vapour pressure with formula for it
3 Likes
it was the water vapour pressure formula and using exp in the tag that fooled me!
thanks again
4 Likes
Do not forget to add formulas for both unit systems and alternate them using #UNITSYS# tag, if you plan on publishing it, or there will be nonsensical results.
3 Likes
Yes indeed - there will be imperial and metric choices. I do intend to publish 
3 Likes
So.
Humidity was 70% so this gives me:
(round(6+0.33*70/100*6.105*exp(17.27*6/(237.7+6))-0.7*122.3-4))Which is a feels like of -81. I did nip out for 10 mins for some wave shots of the water 100m out near high tide as it was blowing towards show but only felt like -5 to -10 minimum
2 Likes
Gosh . Dedicated Testing .
1 Like
There was no way I was gonna miss my first chance to deliberately be out in a 75+mph gale. The gust were pretty exhilarating but after 10 minutes I feared not having the ability to hold onto my phone in sub zero (but not -81) chill.
Las time was accidental during hurricane Bawbag and it was only 45mph horizontal hale that time.
1 Like
2 Likes
I was going to say I am not that stubborn but I now have some extreme raw numbers to plug in and I don’t trust the exp() function in Facer because it relies on interpretations of a constant so if the formula calls for x^y I’ll try again for x**y
I am thinking that if we go back to **0.16 we will be goodbut I have beeen awake for 70 hours now and the caffiene is failing but I don’t think today’s windchill was -81°
I think the idea is to work with the links we have (with or without humidity) and know that in Facer 2**3=8 (2^3) and 50**0.16*=1.86997241771 Google Calc
1 Like
