Topic: CBI/Smokey Bear is there a more accurate script?

[sam2004gp]

I have been using a "modified image version" of the CBI/Smokey Bear Script for a few days with no problems.  But because of high winds in my area the NWS has issued a "Red Flag Warning with Critical Fire Weather Conditions".

Naturally my "modified image version" of SLOweather's CBI script does not show this.  Is there anyway to modify this script further to also use windspeed as a factor in the index?  Also how are the CBI numbers actually displayed under the "normall" Smokey/Sign Combo image?  Mine does not do this.

Or is there any another "index" and PHP script that may show a more accurate representation of the "fire risk conditions"?

Again I would like to display the status of the "risk" at the top of my page as it is now.
www.mountcrawfordweather.org

[SLOweather]

I'm not sure "accurate" is the best term to use in this case. There are several different fire danger or fire weather indexes in use around the world:

The CBI
Angstrom Ignition Index
Fosberg Fire Weather Index
Fosberg Fire Weather Index with Fuel Availability Factor
Equilibrium Moisture Content
Nesterov Index
Keetch-Byram Drought Index (KBDI)
Canadian Fire Weather Index
Haines Index (Upper atmosphere stability)

Some of these are rather simple, some are quite involved. The Canadian FWI, especially, is extensive. I believe I counted something like 35 equations in it. Except for the CFWI, they all tend to measure one or two aspects of fire ignition or behavior. Some can be calculated just from current data. Some, like the KBDI and Nesterov, require yesterday's value as an input to today's calculation

Based on your comments, you might be interested in the Fosberg Index, "a measure that reflects expected flame length and fuel drying based on wind speed, temperature and humidity.  High values indicate high flame lengths and rapid drying."

The formula and discussion are available at http://www.atmos.washington.edu/mm5rt/descript/definitions/fosbergindex.html

Programming it is a joy in math and decision making. Here're the formulas from the link above:

---

FFWI = n*[(1+U^2)^.5]/0.3002

where U=wind speed in mph and n=moisture damping coefficient.

n=1-2(m/30)+1.5(m/30)^2-0.5(m/30)^3

where m=equilibrium mositure content.

for h < 10 %

m=0.03229 + 0.281073h - 0.000578hT

for 10% < h <= 50%

m=2.22749 + 0.160107h - 0.01478T

for h > 50%

m=21.0606 + 0.005565H^2 - 0.00035hT - 0.483199h

where T=temperature in F and h=relative humidity in percent.

[sam2004gp]

Yep a whole lot math there indeed.  Hmm, what to do, what to do.

[SLOweather]

BTW, Red Flag criteria seem to vary by NWS forecast area. What's considered RF in LA isn't the same as north of me in Cambria. Makes writing a Red Flag script a little harder.

[Arthurhh]

I have been using a "modified image version" of the CBI/Smokey Bear Script for a few days with no problems.  But because of high winds in my area the NWS has issued a "Red Flag Warning with Critical Fire Weather Conditions".

Naturally my "modified image version" of SLOweather's CBI script does not show this.  Is there anyway to modify this script further to also use windspeed as a factor in the index?  Also how are the CBI numbers actually displayed under the "normall" Smokey/Sign Combo image?  Mine does not do this.

Or is there any another "index" and PHP script that may show a more accurate representation of the "fire risk conditions"?

Again I would like to display the status of the "risk" at the top of my page as it is now.
www.mountcrawfordweather.org

I get my FWI value from Weather Display, which does a very good job of calculating it.
Mind you I still end up fine tuning what I display since the guys who set the sign boards for the public dont exactly go by the numbers, it may be extreme and we get a little rain technically it is still extreme (by calc) but the guys drop the board back a notch as that is what the public percieve it should be.
Its a losing battle to try and match what is reported by others

[SLOweather]

I get my FWI value from Weather Display, which does a very good job of calculating it.

I believe WD calcs the CFWI...