Anyone know how frostbite thresholds are calculated?

[SMcNeill]

Something small I was working on to go with my home weather system:

Code: (Select All)

SCREEN _NEWIMAGE(800, 600, 32)
$COLOR:32
PRINT "  ";
count = 1
FOR temp = 40 TO -45 STEP -5
    LOCATE , 4 * count
    PRINT temp;
    count = count + 1
NEXT
PRINT


FOR windspeed = 5 TO 60 STEP 5
    COLOR White, Black
    PRINT windspeed;
    COLOR Black, SkyBlue
    count = 1
    FOR temp = 40 TO -45 STEP -5
        wc& = WindChill(temp, windspeed)
        LOCATE , 4 * count
        count = count + 1
        SELECT CASE wc&
            CASE IS > -18: COLOR Black, LightBlue
            CASE IS > -32: COLOR White, SkyBlue
            CASE IS > -48: COLOR White, Blue
            CASE ELSE: COLOR White, Purple
        END SELECT

        PRINT wc&; " ";
    NEXT
    PRINT
NEXT

COLOR White, Black


FUNCTION WindChill& (temp AS _FLOAT, windspeed AS _FLOAT)
    WindChill = 35.74 + 0.6215 * temp - 35.75 * windspeed ^ 0.16 + 0.427 * temp * windspeed ^ 0.16
END FUNCTION

Now, as you can see, my chart matches the values from the chart here: WindChill (weather.gov)




Only issue is my color values don't match.  Anyone know why -62 windchills are light blue at the top of the chart, but then are purple at the bottom?  If the implied temperature is -52 in both cases, shouldn't frostbite occur at the same time?  Isn't that basically what windchill is for -- to give an equal representation of what the temperature would feel like it the wind wasn't blowing?

How's that frostbite time calculated?  Anyone have a clue, just so I can get my color scheme to match?

[doppler]

@SMcNeill

How's that frostbite time calculated?

Dark history behind that one.  WW II Nazi experiments to determine down pilots survival time in North Sea's of England.  They just kept going until the curves emerged.  BTW, they did not use German pilots for this test.  They did use Germans/Polish undesired people.

After the war the most dark part took place.  Allied forces just used the data and said nothing about how it came into existence.

[SMcNeill]

@SMcNeill

How's that frostbite time calculated?

Dark history behind that one.  WW II Nazi experiments to determine down pilots survival time in North Sea's of England.  They just kept going until the curves emerged.  BTW, they did not use German pilots for this test.  They did use Germans/Polish undesired people.

After the war the most dark part took place.  Allied forces just used the data and said nothing about how it came into existence.

Is there some formula for it, or am I going to be stuck with just a whole bunch of IF..THEN type statements to make the chart align properly with the color scheme?

[Dimster]

From what I've read -16.6(f) = frostbite within 30 minutes : -40(f) = frostbite within 10 minute : Any temp below -31 = frostbite but there is also a number a factors that qualify all those values. ie your age, weight and if the wind is constant. I have not found anything on the speed of the wind as it relates to the drop in temperature on exposed skin.

I'm not sure I'm reading your chart correctly but is there a time element on your chart or are all the values we see temperatures? Across the top I do see the x axis is a range of F-Temps but the y- axis isn't clear. Is there a Time value for the exposure to bare skin on the y - axis? I'm thinking your y-axis is wind speed?  

I find your chart "right on" if all the values are just expressions of Temperatures. I don't see a -62 wind chilled temp in the light blue. The worst case I see in the light blue is the column for F 5 degrees, can get down to a feels like F -17 degrees.

[bplus]

What is wrong with loading of IBB thumbnails, no longer work?
I am trying to compare your chart to one I found for WindChill
https://www.almanac.com/windchill-chart-united-states

Windchill:
Wind Chill = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16)
T is the air temperature in degrees Fahrenheit, and V is the wind speed in miles per hour.

Frostbite numbers might be from WW2 data, because Google is being dumb about it.

[Jack]

I think that bplus has the right idea, as sick as I am of reading about ChatGPT this ChatGPT that, here's what it says about SMcNeill's queastion

Frostbite thresholds are determined based on several factors, including air temperature, wind speed, humidity, and duration of exposure. These factors can affect the rate at which heat is lost from the body, leading to the development of frostbite. The most commonly used method to calculate the frostbite threshold is by using the Wind Chill Index, which takes into account both air temperature and wind speed. Other factors such as clothing and activity level can also impact the threshold. The exact calculation of the frostbite threshold can be complex and may vary depending on the specific conditions.

[mnrvovrfc]

I think that bplus has the right idea, as sick as I am of reading about ChatGPT this ChatGPT that ...

Now you've reached Woodrow Wilson's lucky number. Cannot say enough the second half of what was quoted.

[Kernelpanic]

Windchill:
Wind Chill = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16)
T is the air temperature in degrees Fahrenheit, and V is the wind speed in miles per hour.

The question is: how do you put the brackets? 
(Calculation of WindChill - felt temperature)

Code: (Select All)

$Console:Only

Option _Explicit

Dim As Double windChillC, windChillF, temp, windV
Dim As Double fahrenheit, celsius

windChillC = 13.12
windChillF = 35.74

Locate 2, 3
Print "Berechnung des WindChill - gefuehlte Temperatur"

Locate 4, 3
Input "Temperatur              : ", temp

Locate 5, 3
'Kilometer pro Stunde
Input "Windgeschwindigkeit (KM): ", windV

windChillC = windChillC + (0.6215 * temp) - (11.37 * (windV ^ 0.16)) + ((0.3965 * temp) * (windV ^ 0.16))
fahrenheit = (windChillC * 1.8) + 32

windChillF = windChillF + (0.6215 * temp) - (35.75 * (windV ^ 0.16)) + ((0.4275 * temp) * (windV ^ 0.16))
celsius = (windChillF - 32) * (5 / 9)

Locate 7, 3
Print Using "Gefuehlte Temperatur ###.## Celsius. --> ###.## Fahrenheit"; windChillC, fahrenheit

Locate 9, 3
Print "Berechnung nach Fahrenheit"
Locate 10, 3
Print Using "WindChill Temperatur ###.## Fahrenheit. --> ###.## Celsius"; windChillF, celsius

End

[bplus]

Code: (Select All)

Input "Farenheight temp"; T
Input "Wind MPH"; V
Print Wind_Chill(T, V)

Function Wind_Chill (T, V)
    Wind_Chill = 35.74 + 0.6215 * T - 35.75 * (V ^ 0.16) + 0.4275 * T * (V ^ 0.16)
End Function

   

Please don't grade me on spelling ;-))

The question is: how do you put the brackets? 

[SMcNeill]

Guys??...

I've had the windchills calculated properly, even in the original post above.  My question was about the frostbite times, which are from our colord zones and which don't make much sense.

For example, look at a temp of -35 and a windspeed of 5 mph.  The windchill is -52, but the frostbite time is over 30 minutes of exposure.

Now, look at a temp of -10 and a windspeed of 60 mph.  The windchill is only -48, so it's relatively warmer than the above, yet the frostbite time is less than 5 minutes here.

Calculating the windchill values is just a very simple and straightforward equation, but frostbite times aren't explained anywhere at all, as far as I can tell.

At this point, I think the colorization of the chart is going to just have to rely on a crapload of IF style statements to make it match the official version.