Welcome to the Cumulus Support forum.

Latest Cumulus MX V3 release 3.28.6 (build 3283) - 21 March 2024

Cumulus MX V4 beta test release 4.0.0 (build 4017) - 17 March 2024

Legacy Cumulus 1 release v1.9.4 (build 1099) - 28 November 2014 (a patch is available for 1.9.4 build 1099 that extends the date range of drop-down menus to 2030)

Download the Software (Cumulus MX / Cumulus 1 and other related items) from the Wiki

A question about wind chill

Talk about the weather
Post Reply
RayProudfoot
Posts: 3372
Joined: Wed 06 May 2009 6:29 pm
Weather Station: Davis VP2 with Daytime FARS
Operating System: Windows XP SP3
Location: Cheadle Hulme, Cheshire, England
Contact:

A question about wind chill

Post by RayProudfoot »

Wind chill is a constantly changing value depending on the strength of the wind in cold conditions. My Davis VP2 console shows Wind Chill but it's not being updated with each update of the wind - every 2.5 secs.

But on my WUnderground site it is being recalculated with each change of wind. Why isn't the the Davis VP2 console updating more frequently?

https://www.wunderground.com/personal-w ... =ISTOCKPO4
Cheers,
Ray, Cheshire.

Image
User avatar
mcrossley
Posts: 12689
Joined: Thu 07 Jan 2010 9:44 pm
Weather Station: Davis VP2/WLL
Operating System: Bullseye Lite rPi
Location: Wilmslow, Cheshire, UK
Contact:

Re: A question about wind chill

Post by mcrossley »

I thought it was normally calculated on the average wind speed, which doesn't change rapidly. Sounds like WU may be calculating it on the instantaneous speed?
RayProudfoot
Posts: 3372
Joined: Wed 06 May 2009 6:29 pm
Weather Station: Davis VP2 with Daytime FARS
Operating System: Windows XP SP3
Location: Cheadle Hulme, Cheshire, England
Contact:

Re: A question about wind chill

Post by RayProudfoot »

That would explain the lack of updates on the console. Bit disappointing because gusts could create a new record which will be missed if only average wind is used. :(
Cheers,
Ray, Cheshire.

Image
User avatar
mcrossley
Posts: 12689
Joined: Thu 07 Jan 2010 9:44 pm
Weather Station: Davis VP2/WLL
Operating System: Bullseye Lite rPi
Location: Wilmslow, Cheshire, UK
Contact:

Re: A question about wind chill

Post by mcrossley »

It would bounce around all over the place though if it used the instantaneous speed.
RayProudfoot
Posts: 3372
Joined: Wed 06 May 2009 6:29 pm
Weather Station: Davis VP2 with Daytime FARS
Operating System: Windows XP SP3
Location: Cheadle Hulme, Cheshire, England
Contact:

Re: A question about wind chill

Post by RayProudfoot »

Yes but it would correctly show the actual wind chill. And it's only shown to a whole number so no more so than the wind value constantly changing.
Cheers,
Ray, Cheshire.

Image
User avatar
mcrossley
Posts: 12689
Joined: Thu 07 Jan 2010 9:44 pm
Weather Station: Davis VP2/WLL
Operating System: Bullseye Lite rPi
Location: Wilmslow, Cheshire, UK
Contact:

Re: A question about wind chill

Post by mcrossley »

You could argue that the average speed is a better value, body chill takes effect over a period of time of exposure, you aren't instantly chilled in a few seconds. Though you may feel an icy blast! :lol:
RayProudfoot
Posts: 3372
Joined: Wed 06 May 2009 6:29 pm
Weather Station: Davis VP2 with Daytime FARS
Operating System: Windows XP SP3
Location: Cheadle Hulme, Cheshire, England
Contact:

Re: A question about wind chill

Post by RayProudfoot »

Good point Mark. :D
Cheers,
Ray, Cheshire.

Image
User avatar
jdc
Posts: 142
Joined: Tue 19 Jun 2012 8:51 pm
Weather Station: Davis VP2 : Instromet
Operating System: Win 10
Location: Portsoy,.
Contact:

Re: A question about wind chill

Post by jdc »

It's always described as an 'indicator' as to the effects of wind at low temps and varies depending on sunshine too, so seems fairly imprecise to start with. I think it is primarily for use in regions where temperatures are less than -10 and where the wind is probably more linear.
Extract (part) from 'Marine Observers Handbook' :
It can be measured by the rate of heat loss per unit area, the "windchill factor" or more commonly by the "windchill equivalent temperature" (WET). No allowance is made for precipitation or sea spray. Windchill does not apply to inanimate objects, even heat producing engines. In "full" sunshine, a correction of about +7°C at low wind speeds and +3°C at gale force should be made.
RayProudfoot
Posts: 3372
Joined: Wed 06 May 2009 6:29 pm
Weather Station: Davis VP2 with Daytime FARS
Operating System: Windows XP SP3
Location: Cheadle Hulme, Cheshire, England
Contact:

Re: A question about wind chill

Post by RayProudfoot »

Thanks John. I don't have any sunshine recording hardware but even if I did it seems unlikely the Davis software could use it.

Most of the time WC is not an issue in the British Isles at sea-level or thereabouts. Just for a few days in the year when we have very unusual conditions.
Cheers,
Ray, Cheshire.

Image
Post Reply