First of all: extreme high values in the high register (so, above 950/1000 as I see it now, this is not fixed yet) seem normal for a region like yours and july 27 is at hight of summer. But to be honest, I did not expect these to be so high when I started out and had only roughly an idea of the output of the calculations.
In Australia a class has been added above red: purple and they name it catastrophic
. Phil's site
also has weather like this in summer (now approaching over there). Catastrophic
would mean that ignition could be by a spark or a flash of lightning. It is likely I will add that class as well for everything above 950/1000 (those figures are far from definitive yet) and maybe adjust the current classes a bit. That depends also on your fire statistic, if any. Most other fires - in the lower region of the warning levels - have human origins.
NOTE: in my blog on my first evaluation
of the algorithm (which I did with an old version of the program and a slightly different algorithm, so different absolute values) I noted the following:
- Danger level: LOW: The fuel is wet, no drying has taken place.
- Danger level MODERATE: The combination of wind, humidity and temperature favour a drying process which has started.
- Danger level: HIGH: The drying process has continued and is basically complete. Little humidity left in litter and surface of wood.
- Danger level: VERY HIGH: Last stage of the drying process, fuel has become easily inflammable. Ponds are falling dry.
- Danger level: EXTREME: Drying has completed, no moisture left in fuel. Fuel easily inflammable, a spark can ignite it. Almost explosive.
Apparently I overrated the red class.
In your region you had no rain for 68 days(!!) and temperatures are well in the 30 degrees approaching and reaching 40. That means the drying process really is finished. There is no more water to vaporise, vegetation is in survival mode (closed stoma
so no water coming from plants), the soil is exhausted and the only moisture around is via air transport. It is difficult to estimate, but I assume the moisture you see is because the wind comes from sea and is not from the soil or the vegetation. The whole play is difficult to assess, but from what I have seen now, everything above combines into extremely high figures for the pwsFWI assessment.
In short: Yes, it surprised me to see those high figures, but they appear to be 'normal' during prolonged dry periods in hot, semi-arid area's.
But now I am interested: were there fires in your region in that period? And if yes: how many, which dates, how large area?
Is there a fire statistic for a circle of 50 - 100 km around you? Could you summarise that in short here?
And a next step: are there other weather stations you know with similar weather and running Cumulus(MX)? Especially semi-arid conditions are interesting. Spread the word!
Thanks for your first analysis.