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Change of release post on Cumulus Support forum

Since 21 april 2020 CumulusUtils has its own subforum on the Cumulus Support forum. That makes things clearer and creates better oversight. However, many links in the blogs before that date contain a link to the old release topic. I did change some recent ones but left the older topics untouched. If you encounter such link, remember to go here and not there.

About pwsFWI

pwsFWI is now a bit more than a year old and has proven its value : it relates very well to the existing indices and the EFFIS Current Situation viewer. This means that the note : Behavioural testing still under way! will be removed from the pwsFWI page at the end of the European fire season (21 September).

Having said that, I have noticed that some users have reverted to the FWI calculations and graphs as shown by FWIcalc  as if that one is better than pwsFWI.

Or more valuable.
Or more standard.

I would like to comment on that.

  1. Although the numeric values of the two differ, intentionally, both indices indicate the risk of wildfire very well. Having followed both values in different places, I would even say that pwsFWI performs better, meaning it is more accurate and requires no human interaction.
  2. FWI in the version of FWIcalc calculates and displays more than just FWI, it also gives the possibility to show the sub-indices (see the article on the Canadian FWI). That is nice but does not make interpretation easier for the non-specialist that most weather station owners are: fuel amount, fuel type, inclination, geography, moisture content of litter, drought in general and the summation / integration of the sub-indices? What is at play?
  3. Even while the Canadian FWI is heavily used by the larger institutes you must be very aware that FWI requires a typology of fuels and land use types. That makes it difficult to configure and more specific to certain regions of the world (less for Europe). On the larger scale it also requires a formidable manpower, registration, administration and computer and satellite systems.
  4. pwsFWI just requires some meteorological input to achieve to similar output. It is the humidity that counts: wet would does  not burn!

Having said that, it must also be seen that pwsFWI is not just a development by some amateur without any foundation, pwsFWI as it stands is a member of a family of Fire Weather Indices and fire simulation software based on Vapour Pressure Deficit and other drought indicators all over the world. I mentioned those developments in other forum posts and blogs but will repeat and summarise here:

  1. The original authors (see my initial blog on the subject) use their calculations for climate research . Their index is called the HDWI (Hot Dry Windy Index) and their site is here.
  2. An explicit VPD application is in the study of Impact of Anthropgenic Climate Change on Wildfire.
  3. Another approach lies in the simulation software used by fire research and fire fighting research as indicated by Adrián Cordil in my blog  on PyrolifeITN.
  4. A fourth application of VPD can be seen in the Forecast application of SpotWx. They publish exactly those data pwsFWI requires for its calculation. That is not a coincidence even if it is for use in FFMC and Prometheus. The Prometeus application (pdf!), for which SpotWx publishes its table, is a sophisticated modelling tool which mainly uses the FFMC out of the Canadian FWI for its application of meteorological data. As such the weather estimation part in Prometheus can be seen as a crossover with any VPD based approach.

All approaches use temperature, wind, Relative Humidity and rainfall as parameters for more or less complex calculations regarding fire risk. As such, pwsFWI is member of a larger family of calculations which all behave similar. Note that the Prometheus software mentioned above uses a 100 km validity range when it is based on one (1) station. while I claim 50 to 200 km as a valid range for pwsFWI depending on local geography and micro-climatology. To be estimated by the station owner.

The big difference of pwsFWI with all FWI and climatology based systems is that pwsFWI is limited to a local situation and much simpler to derive. Therefore it is fit for personal weather stations and FWI actually is not. FWI requires a big system of computers, paperwork and people to create it and to handle it. Despite the suggestion that the index can be easily determined. the number and complexity of its parameters show the opposite.

In addition I would like to remark that, to my personal opinion, the validity of Fire Weather Indices, especially FWI, used in Fire modelling systems are stretched beyond their validity when used for operational work with hourly values. Yes, wind can vary quickly and has major influence on the development of wildfire and as such the parameter has importance. But to think you need a computer to estimate the wind effects in the field in an operational situation, is beyond reason: firefighters  should trust their own judgement of the weather and not a (field) computer.

Fire fighting needs common sense, knowledge of meteorology and ecology and not computers.
Computers and simulation are good for study and education.
Fire Weather Indices are warning level indicators, nothing more.
And they are more needed with climate change creeping northbound.


On PyroLife ITN, Tecnosylva and Wildfire Analyst

This is a short blog on some fire related research and organisations. Unrelated directly to pwsFWI but definitely useful to follow if you are interested in fire – wildfire and/or society related issues regarding large wildfires. Especially the running webinars are interesting (and free) !

Recently (in  2019) an ITN project PyroLife started (what does ITN stand for btw?), led by Wageningen scientist dr. Cathelijne Stoof.

Apart from being a great initiative, it became quickly very interesting because of the free webinar which started 3 June 2020 (and running till the end of july 2020). The presentations of this Symposium are published on the YT channel of PyroLife (don’t start binge watching these presentations, prevent overkill).

I would like to point to the the presentation of Adrián Cordil of 10 June 2020 (at moment of writing not yet published) on thePyroLife YT channel linked above, scientist at the University of LLeida, Spain and associated with Tecnosylva S.L. (twitter account). He presented the work of Technosylva regarding simulation software, put to work in different parts of the world in the context of combatting wildfire situations.

Estimating Fire Weather is one aspect of this. An interesting piece  of software to look at is Wildfire Analyst also available for Android. Check it out.

pwsFWI is unfortunately not related to this [large] project, but the results of your weather  station, and your understanding of meteorology, definitely might give you an entry to understanding what they are doing there in Spain.

On the programming of CumulusUtils (2)


More than 6 months ago, I wrote a blog  on the how and why of the programming of CumulusUtils. It is time to do that again because in 6 months, over the winter and now deep into the Corona Virus crisis, a lot has happened with CumulusUtils. When I wrote the first blog, it was mainly about the inspiration and development of pwsFWI. And it still is the most important module of the whole program (at least, it is for  me). But while working on pwsFWI and seeing where it was deployed  triggered something. Beside having the pwsFWI, one needs to think about the weather. It is not just a black box, it is about understanding the weather and it’s effect on vegetation and animals (including humans). To understand the weather you need to look at the parameters, the measurements. Continue reading

Impact of anthropogenic climate change on wildfire

I designed and developed my Fire Weather Index (FWI) for Personal Weather stations (PWSs) starting with basic logic reasoning (wet wood does not burn), with scientific background and made it usable in the context of PWSs. I found a very interesting and confirming article from October 2016: Impact of anthropogenic climate change on wildfire across western US forests [1].

Continue reading

Analysis of pwsFWI prediction


In my previous blog I described why and how the predictions on pwsFWI were implemented. Also I promised a short analysis:

We’re now in version 1.8.3 and it seems all to be working OK. The testing is back on the meteorological level, trying to find out how much a two day ahead prediction will differ from the actual calculation when the day has past.

In this blog I will show the results and try to interpret them.
Please note that this is not a scientific or even a full analysis as I am lacking the resources and the data for that.

Continue reading

Predictions of pwsFWI


The past months I blogged several times about my Fire Weather Index for personal weather stations on the basis of Cumulus as data acquisition software. So if you’re new here and don’t know what pwsFWI is about, check out the previous blogs on the subject. Currently, pwsFWI is part of a small software package named CumulusUtils. This meteo website/blog is the home of the package which is distributed through the Cumulus support forum. If you have a weather station which can cooperate with Cumulus, don’t hesitate and get it, it’s free.

Continue reading

Winter is coming

Last night Daylight Saving Time switched back to its winter position. That itself is nothing special. Well, maybe it is because the EU is really thinking of abandoning the twice per year hour shift, it is biologically deregulating.

But that is not why I write this [short] message. The switch itself showed up nicely on the temperature graph of my weather station and, as if it was saying Winter is Coming, exactly on the time of the hour switch, the temperature fell from 15 to 10 degrees within an hour and a half.

It shows all nicely on the chart (after the break). Continue reading

Behaviour of pwsFWI with first rain

One of the goals of the current implementation of pwsFWI is to see its behaviour under all conditions. It is therefore very interesting to see that behaviour in the two stations in semi-arid zones (in Australia and in Spain) where long dry periods may suddenly alternate with rain after which the drought returns. Continue reading