Wind Chill Calculation

[werribee_au]

The wind chill here jumps around a little.

I have not set the 10 °C limit in the ini file, but I suspect that the 4.8 km/h is causing this.

I have set 'calculate 10 min wind average' and 'use speed for average calculation'.

Does the wind chill calculation use the average speed?
Is there any undocumented ini setting/value that I can use to change the 4.8 km/h setting?

[steve]

Does the wind chill calculation use the average speed?

Yes.

Is there any undocumented ini setting/value that I can use to change the 4.8 km/h setting?

No. The problem is that wind chill is only defined for wind speeds above 4.8 km/h - at lower speeds it is deemed to have no effect. If I offered the option of a different cutoff, you would get numbers but they wouldn't mean anything. So while it would be an easy change, and I don't mean to be unhelpful, it wouldn't really be correct to offer it.

It does mean that when the wind speed hovers around 4.8 km/h, you get this disjointed effect in the graphs, unfortunately.

It is possible, of course, that there's a bug which is making things worse than they ought to be. Looking at your current graphs on your web site does make me wonder.

wind.png

Your wind speed seems to be above 4.8 for (at least) the period 22:00 to 03:00. But your wind chill keeps reverting to ambient temperature briefly several times during that period:

temp.png

That seems a bit strange...

It looks like the data before about 02:00 came from the logger - or the Cumulus log files, at least (i.e. you restarted Cumulus at that point). But even after that, it doesn't seem right. Could you upload your July log file - you could just extract today's data, or attach the entire file.

[werribee_au]

Thanks Steve,

You are correct with the 2am comment as I have a scheduled reboot of the station pc at 2am each morning.

Attached is the July log for the 19th & 20th

Thanks

[Super-T]

Why was it that you found it necessary to reboot at 2am??

[werribee_au]

Why was it that you found it necessary to reboot at 2am??

I have found that it keeps things fresh rather than letting the computer carry on for days or weeks.

We use this process for the embedded pc's at work with a daily data backup, but of course when cumulus shuts down it automatically creates a backup. It also facilitates an automatic daily backup of data (In the Cumulus backup sub-directory) which I can use if there are any issues I need to correct.

If you wish to use windows scheduler to do this I may be able to help you with the settings etc.

EDIT:Sorry I didn't answer the question you asked. Why 2am? I'm asleep (Well I should be). To be honest it is a legacy thing, is is the time we use at work and in the car wash industry there are very few transactions at that time of the morning.

[steve]

Attached is the July log for the 19th & 20th

Thanks, I understand what's happening now. Cumulus calculates the wind chill as soon as it reads data from the station - using the wind and temperature figures that it has just read. You've opted to get Cumulus to calculate the average wind speed, so the wind speed on your graph is not the same as the speed which is being used in the wind chill calculation. The station's version of the wind speed must keep falling below the 4.8 km/h threshold, so the wind chill keeps reverting to ambient temperature.

It seems to me that what really should happen is that if you have opted to have Cumulus calculate the average wind speed, it should use that value, and not the station's value, in the wind chill calculation! I will implement this for the next release.

[werribee_au]

Excellent!

Thanks for the explanation!