Windchill

[daj]

I was doing some research into Windchill and Heat index for my own education, and in the process I wrote a small summary of each on the Wiki.
http://wiki.sandaysoft.com/index.php?title=Wind_chill

One of the things which I find in several places I have read is that Windchill is only calculated at temperatures below 10C (50F).

I note that Cumulus is today reporting my Outside temp as 13.4 and Windchill as 13.2.

windchill-screenshot.png

Just to be clear, Cumulus calculates my Windchill as my station can not.

What are other peoples thoughts on Windchill and when it should be calculated?

[steve]

Cumulus has an ini-file option ("UseWindChillCutoff=1" in the [Station] section) which does this (i.e. stops the wind chill calculation above 10C).

One day I really will find time to document the undocumented ini-file options!

[daj]

thanks --- It wasn't a criticism of Cumulus; more that I wanted to understand Windchill.

useful tip however

[steve]

Yes, understood, it was just my contribution to the discussion

I know that wind chill calculation is a controversial area, and that there is/has been more than one 'official' formula. I have a feeling that both the 'old' and 'new' formulae are lurking in Cumulus and I should really rationalise it.

[kiwi_steve]

Long time lurker, first time poster

I've been looking at this stuff for a while now, and finally bought a weatherstation just before christmas... for my Dad... but hey, its still one I can access and tinker with...

Because I wanted to incorporate specific information into his existing website, and in his specific format, I was using some PHP code (its a Drupal CMS site) to borrow readings from the realtime.txt file (more on that in the homebrew section later)... but couldn't positively identify the windchill reading in that file... so I started researching it to calculate it within the page itself from wind speed and temperature and found the following:

- 42oC to +4.4oC & wind speeds between 5 and 100 km/hr

It came from this page:
http://home.iprimus.com.au/foo7/windchill.html

And was the only "metric" version I could find. It also has an interesting historical account of windchill.

regards

Steve

[gemini06720]

For anyone interested, I found, at the very least, the following two links to Environment Canada:

http://www.pnr-rpn.ec.gc.ca/air/winters ... ll.en.html

http://www.msc-smc.ec.gc.ca/education/w ... g_10_e.cfm

And if someone want to calculate the wind chill at his/her station, here is it is done:

WC (metric) = 13.12 + 0.6215 * Tair - 11.37 * V 0.16 + 0.3965 * Tair * V 0.16

-- where Tair = air temperature (C), V = wind (km/h)

WC (imperial) = 35.74 + 0.6215 * Tair - 35.75 * V 0.16 + 0.4275 * Tair * V 0.16

-- where Tair = air temperature (F), V = wind (mph)

Those formulas and more information is also available on Wikipedia: http://en.wikipedia.org/wiki/Wind_chill

[beteljuice]

From Cumulus help

log files / realtime.txt
....

24 57 inside humidity
25 3.6 wind chill
26 -0.7 temperature trend value

...

'Field' 25 is array[24]

[daj]

Hi Kiwi Steve and welcome to the forum

The Wiki is your friend

http://wiki.sandaysoft.com/index.php?title=Realtime.txt

[kiwi_steve]

Its funny how much work I could have saved myself by simply reading the instructions

Still, I learnt a bit doing it the hard way... and I'll post what I have done over in the homebuilt section so others can tinker with it if they like...

Steve