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Windchill

Posted: Sun Jan 27, 2008 12:06 pm
by pirelli
I always like to look at the windchill on my basestation (WMR100) to see how cold it \"really is\" outside.

Since the dashboard came along I've been looking at that instead, but yesterday I noticed that there is something wrong since I don't have the same numbers there compared to the basestation.
For example: 3.5 degrees Celsius, 4.7 m/s and chill equals -3.3. Then suddenly it blows at 4.5 m/s and I have a chill of -1.7.
If that is a calculated value and not retrieved from the WMR100, can there be some fault in the formula?
If I do manual calculations with the help of Osczevskis och Bluesteins formula I get readings that looks like the ones I see in my basestation.

Thanks,
Lars-Inge = L-I = Elli = Pirelli

Re:Windchill

Posted: Sun Jan 27, 2008 7:55 pm
by admin
wind chill computation is done by this formula:
w = 33.0 + ((0.478 + (0.237 * sqrt (s)) - (0.0124 * s)) * (t - 33.0))

w = wind chill in °C
s = wind speed in km/h
t = temp in °C

as an alternative I have found this one:
w = (13.12 + (0.6215 * t) - (11.37 * pow (s, 0.16))) + (0.3965 * t * pow (s, 0.16))

any preferences?

Re:Windchill

Posted: Sun Jan 27, 2008 10:23 pm
by pirelli
That's the old formula you are using then. The alternative looks like the one that give me the correct numbers.
Wikipedia says it all: http://en.wikipedia.org/wiki/Windchill

Re:Windchill

Posted: Sat Feb 02, 2008 2:12 pm
by pirelli
Anything new about the windchill calculation?
1.4 Celsius temp
6.3 m/s gustwind
give -8.8 chill in dashboard

while at the wmr100 it shows -4
and wunderground says something like -3

Thanks,
Pirelli
with a licensed meteohub:woohoo:

Re:Windchill

Posted: Sat Feb 02, 2008 3:51 pm
by admin
Give 1.8b a try.

Re:Windchill

Posted: Sun Feb 03, 2008 12:07 pm
by pirelli
Now I've tried both 1.8b and c and they are giving the wrong numbers compared to when I calculate manually.

Dashboard:
6.5 m/s
5.2 temp
-4.1 chill

Manually gives me chill= 0,9

Strange

Re:Windchill

Posted: Sun Feb 03, 2008 5:55 pm
by admin
Hi,
I just checked the code and found out that the the new formula didn't made it into the update. Sorry for that. The code is there, but was not activated :-(

It will be in the next update, which will be a pure bug fix update soon to be released. Thanks for spotting this!

Re:Windchill

Posted: Tue Feb 05, 2008 7:07 pm
by admin
New formula doesn't make it into 1.8b. Will be there in 1.8d

Re:Windchill

Posted: Tue Feb 05, 2008 8:23 pm
by pirelli
Nice!
Thanks!!