Live FWI

[cyclone]

I know the FWI is updated once a day, but i've managed to grab a code for live FWI.
it is used here example: http://www.weatherzone.com.au/station.jsp?lt=site&lc=31210&list=ob

here is the code:

FFDI = 2*exp(-0.45+0.987*log("Drought"))-0.0345*RH+0.0338*"Temp"+0.0234*"Wind")

where

"Temp" = temperature (C)
"Wind" = Wind speed (km/h)
RH = relative humidity (%)
"Drought" = Drought Factor

If Temp, Wind or RH are not defined, the calculation returns null.

If Drought is not defined, the calculation uses 10.

what do others think ?

[Weather Display]

interesting Idea
I presume the drought factor is the FFDC value?

[cyclone]

hmmm, i'm not too sure, i wonder if its the The Byram-Keetch Drought Index ??

[cyclone]

hello Brian,
do you require any additional information ?

cheers

[cyclone]

Hello Brian,
Do you think this addition is possible ?

Also does NZ every see very high fire dangers ? don'y hear about  it on tv.

[Weather Display]

really needed to know what to use for drought factor
maybe just use the normal FWI drought code number?

El Nino spring/summer cause high fire risk to eastern parts of NZ
but we have not had a strong El Nino for years

[cyclone]

just got a reply back:

Hi

No idea what you are asking.

The drought factor we use is as per the Macarthur meter. This is a number between 1 and 10. We just assume a worst case of 10 always. The DF can be calculated from a drought index such as KBDI or Mount SDI, but as we don't have access to those numbers either we don't calculate it.
Matt
Chief of Television Services
Head Meteorologist

does it help ?

[Weather Display]

so just set it to 10?

[cyclone]

i suppose we could just use '10'

We have our dry 'fire' season over the next couple months, i can't wait for this addition.
This afternoon we saw the dew point drop suddenly with a slight wind spike.



cheers

[Weather Display]

I have added a custom tag
%liveFWI%
to the latest .zip update
it uses the DC from the normal FWI

[cyclone]

downloaded and testing

[cyclone]

the formula does not appear to be right, so I've asked for clarification.

Hi,

I have had a chat to our processing guys and they have informed me that log should actually be ln i.e. logarithm to base e

This should make a difference to your calculations and should see them match what is on Weatherzone.

Let me know if you still have discrepancies.

Thanks

[Weather Display]

I did wonder what log should be used
I have used natural log
base e log is different again

I will look into changing that for the next update

[Weather Display]

in reviewing my code, I am already using ln (natural log, or log to base e (constant 2.71828183)
when comparing to weatherzone you would need to account for the drought code
they might be using 10 all the time
whereas WD is going to be using the DC value from the WD dervied FWI

[cyclone]

 i think they are using 10 all the time.

the figure i'm getting is around 480-490