### Chandler Burning Index computed by a virtual sensor

Posted:

**Wed Jul 26, 2017 5:49 pm**I wanted to compute the Chandler Burning Index with a virtual sensor. It took more than a few trial-and-error attempts to get it to work and I thought others might be interested in a "how-to".

First of all, this computation is using Meteohub version 4.6t (I don't update often).

For your virtual sensor, define the following:

New ID - data#

Name - CBI or what ever you wish

Trigger - th#

Conversion - awk ' { printf ''%d'', ((((110 - 1.373 * $4) - 0.54 * (10.20 - $3 / 10)) * (124 * 10 ** (-0.0142 * $4))) / 60) * 100 } '

The Chandler Burning Index formula is CBI = (((110 - 1.373*RH) - 0.54 * (10.20 - T)) * (124 * 10^(-0.0142*RH)))/60. Note that the temperature must be divided by 10 and the overall index number multiplied by 100 to produce the correct value. I also could not get the exponentiation symbol "^" to work. It errored as "_". So I switched the formula to a double asterisk "**" which is supposed to be equivalent to "^".

For now, I've been plotting the CBI on a simple 24 hr graph with an explanation of the different color code levels underneath the graph - https://www.tceweather.com/firedanger_graph.html. When I get the time, I'd like to add the fire danger level color codes to the graph some how.

Edit: Fixed the graph link to the permanent version fron the temporary testing one.

First of all, this computation is using Meteohub version 4.6t (I don't update often).

For your virtual sensor, define the following:

New ID - data#

Name - CBI or what ever you wish

Trigger - th#

Conversion - awk ' { printf ''%d'', ((((110 - 1.373 * $4) - 0.54 * (10.20 - $3 / 10)) * (124 * 10 ** (-0.0142 * $4))) / 60) * 100 } '

The Chandler Burning Index formula is CBI = (((110 - 1.373*RH) - 0.54 * (10.20 - T)) * (124 * 10^(-0.0142*RH)))/60. Note that the temperature must be divided by 10 and the overall index number multiplied by 100 to produce the correct value. I also could not get the exponentiation symbol "^" to work. It errored as "_". So I switched the formula to a double asterisk "**" which is supposed to be equivalent to "^".

For now, I've been plotting the CBI on a simple 24 hr graph with an explanation of the different color code levels underneath the graph - https://www.tceweather.com/firedanger_graph.html. When I get the time, I'd like to add the fire danger level color codes to the graph some how.

Edit: Fixed the graph link to the permanent version fron the temporary testing one.