Cumulus Support

Hi Hans

I just downloaded the latest version and looked at various bits. I noticed that the chart covering All PWS FireIndex results looks a bit off with a higher value at the end of the at the year than in mid summer. I know that this year has been particularity damp but my gut reaction is that the index should be high in the summer and very low in the winter especially in the northern hemisphere.

This is the first time I have looked at this chart for a long while so I am not sure when this error started, do you have any thoughts on the matter.

I have attached the Charts definitions file for information.

AndyKF650 wrote: ↑Mon 09 Dec 2024 2:28 pm Hi Hans

I just downloaded the latest version and looked at various bits. I noticed that the chart covering All PWS FireIndex results looks a bit off with a higher value at the end of the at the year than in mid summer. I know that this year has been particularity damp but my gut reaction is that the index should be high in the summer and very low in the winter especially in the northern hemisphere.

This is the first time I have looked at this chart for a long while so I am not sure when this error started, do you have any thoughts on the matter.

I have attached the Charts definitions file for information.

Hi Andy, nice one. There are two things here at play:

1. The value in itself is not very high (66) compared to your calculation in e.g. july 2022 when it was 124 (and even that did not generate an alarm I assume) so I can live with that. It still is a low value and judging the value with complex values of the saturation pressure iis difficult to impossible.
2. The estimation of pwsFWI has more to it than just the calculation. The warning signal comes from a smoothing and averaging method I developed during the testing year in 2019/2020 with the extreme heat in Australia. So the calculation itself has meaning if it would be five days in a row.
3. This calculation has meaning when compared to the published warning signal on your webpage and there you see the effect of the Quenching and smoothing.

In your chart you can see which days attribute to the published pwsFWI but you must be carefull to attribute in itself a warning signal. The calculation was not meant to be judged on a daily basis, but you can see which days contrinute more to the warning signal.

Two wiki pages try to explain the whole thing:

1. https://cumuluswiki.org/a/PwsFWI
2. https://cumuluswiki.org/a/Theoretical_b ... _on_pwsFWI

T.b.h. I have my doubts pwsFWI will ever generate an alarm yellow or higher on the channel islands but with climate changing rapidly you should see values climbing slowly each year. And installations on bigger landmasses would have more severe effects.