Cumulus Support

I've been seeing this behaviour for a long time (a couple of years or more), so thought I should make a post as it looks incorrect to me. The two graphs below show wind speed (10 minute mean) and gusts (10 minute maximum). Logging and plotting interval is one minute.
I don't understand how the 10-minute maximum gust could be less than the mean speed for the same 10-minute period. I notice this behaviour only when wind speeds are decreasing. It is almost as if the mean speeds are "offset" to the right.

If you take a very simple example with a 10 min logging/plotting interval, with a speed of 10 at the start of the period and 5 at the end - and no gustiness/variation. You should have a mean speed of 7.5 for the whole period (plotted at the end of the period), and will have a 10-minute gust speed of 10 (plotted at the end of the 10-minute period).

Or am I missing something?

I suspect a miss set option somewhere. As you say it is just plain wrong. I never see anything like that - https://weather.wilmslowastro.com/graph ... t.php#wind

For the Davis stations "Average Wind Speed" and "Speed for average calc" should both be un-checked

I'll have a dig into the code later.

I assume it has to do with a mix of CumulusMX calculated values and station received values.
I let all values calculate by CMX so that no misunderstanding can take place.

mcrossley wrote: ↑Mon 29 Nov 2021 9:48 pm I suspect a miss set option somewhere. As you say it is just plain wrong. I never see anything like that - https://weather.wilmslowastro.com/graph ... t.php#wind

For the Davis stations "Average Wind Speed" and "Speed for average calc" should both be un-checked

I'll have a dig into the code later.

I had both those options checked. I un-checked them on 30/11/2021 at 07:00. The difference I notice within a couple of hours is a more "blocky" graph for speed - which, I assume, is down to the Davis station rounding its mean speed to the nearest mph. This is a bit annoying, but doesn't bother me massively as long as it is accurate.

I will monitor - especially at times where speeds are decreasing.

The Average Wind Speed is less important - once you have confirmed that the speeds look reasonable now, you could re-enable that if you want the decimal average (I get that from the WLL anyway which does do sensible averaging)

mcrossley wrote: ↑Wed 01 Dec 2021 2:03 pm The Average Wind Speed is less important - once you have confirmed that the speeds look reasonable now, you could re-enable that if you want the decimal average (I get from the WLL anyway which does do sensible averaging)

I re-enabled Average Wind Speed yesterday morning, after running several days and convincing myself that mean speeds were now behaving correctly. The curve has smoothed out nicely so I am happy now.

The mean speed seems much more responsive now, matching with what I observe out the window. I would love to go back and re-run the past 16 months wind speed data with my current settings but that would be impossible. I can think of several windy days last December and February which would benefit from this.

Thanks to all who made suggestions.