Chandler Burning Index

[steve]

gives -0.30516388531598
im not sure why the -

That's not -2 as you said originally, it rounds to zero, which is apparently correct. The formula does give negative numbers for some input values.

[beteljuice]

As possible (and small) negative values are meaningless, and the index is quoted as integer % it would be better to modify the code slightly

Code: Select all

<?php
$ftemp = '73.0'; // why are these numbers in quotes ?
     $rh = '87';
// Convert F temp to C temp
$ctemp = (5/9)*($ftemp-32);     
$ct = round($ctemp,0);  // why are you making this an integer ?

// Start Index Calcs

// Chandler Index
$cbi = (((110 - 1.373 * $rh) - 0.54 * (10.20 - $ct)) * (124 * pow(10,(-0.0142*$rh))))/60;

// new fix
$cbi = round($cbi), 0);
if($cbi < 1) { $cbi = "0" }; // note: formatted as a string to avoid any zero / null possibilities
echo $cbi;
?>

[n9mfk]

Hi All,
I did some research an here what i found
that fwicalc
uses
Daily Chandler Burning Index (primary data) is calculated using...

CBI_D = (0.0167 * (104.5 - (1.373 * H) + (0.54 * T)) * (124 * pow(10,(-0.0142 * H))))

Monthly CBI (only available in web tags) is calculated using (T & H are monthly averages)...

CBI_M = (((110 - 1.373*H) - 0.54 * (10.20 - T)) * (124 * pow(10,(-0.0142*H))))/60
an by this it for monthly http://www.fs.fed.us/psw/topics/fire_sc ... andler1983
I can not find any info for doing a daily value ?

[GraemeT]

Beau,
You're quite correct.
As I understand it, the temperature and humidity values used for daily CBI are the readings taken at midday on the day of calculation and the values used for monthly CBI are the monthly averages taken at midday each day.
I think the idea is to measure the conditions in the hottest part of the day, that way the resultant index value will be the most meaningful.
You will have noticed that FWICalc allows you to define the time the data file is parsed. That time should be after the daily temp and hum values have been read, so that the input data is freshest, giving a more meaningful result.

Here is the relevant section pasted from FWICalc help:

Parse at time: By protocol this should be somewhere around 12:00hrs daily. It should be timed to coincide with the updating of the Data File. ie. If the weather station software updates the Data file at 12:00hrs daily you should set the "Parse at time" to 12:02hrs. FTP could be setup to upload the parsed file to the server at 12:05hrs. FWI CALCULATOR uses the system clock as its basis. If you have any "Graph Layouts" stored all of these will be renewed at this time to the "graphs" folder in the program folder.

As you'll have noticed, FWICalc only starts to give really meaningful results after it's been running for over a month - the time it takes to build a history of average data values to work with.
For that reason, I've opted to use the CBI from FWICalc for a monthly index and for a daily index I use the daily CBI formula with temp and hum readings taken at 1200 hrs each day.

Beteljuice,
A check for cbi < 1 is precisely what I do in my daily routine to avoid a negative index which is, of course, meaningless.

Edit: Also, it should be kept in mind that a CBI less than 50 is rated as LOW. On that basis, the actual numeric value becomes academic, anyway.

[MickinMoulden]

The Chandler Burning Index can be computed entirely using Javascript, I've been doing it for years. You can see a page I have dedicated to real time fireweather at http://www.wilcowx.com/firemet.php. This is a PHP page but only for some other purposes and scripts on the page.

I've been playing with JavaScript to calculate the CBI, but all I get is "Chandler Burning Index". I've used static RH and T figures for testing (as is the "hello"). Here it is:

Code: Select all

<td>Chandler Burning Index</td>
    <td>
<script type="text/javascript">
<!--
	var RH = "5";
//<#hum>
	var T = "40";
//<#tempYH>
	var CBI = (((110 - 1.373 * RH) - 0.54 * (10.20 - T)) * (124 * pow(10, (-0.0142 * RH))))/60;
document.write(CBI);  //Just seeing if it would print the CBI value....it didn't
if(CBI>100){
document.write("CATASTROPHIC");
}else if (CBI>75){
document.write("EXTREME");
}else if (CBI>50){
document.write("SEVERE");
}else if (CBI>25){
document.write("VERY HIGH");
}else if (CBI>12){
document.write("HIGH");
}else if (CBI>0){
document.write("LOW-MODERATE");
}else {
document.write("LOW-MODERATE");
}
document.write("hello");
//-->
</script>
</td>

Obviously using the FDI ratings and values with the CBI formulae is a different issue all together. But what is the fix?

[steve]

pow needs to be Math.pow

[beteljuice]

and .... you've made vars T and RH strings not numeric.

Multiplication and division in the formula will appear to work correctly, but subtraction and addition will not !

[MickinMoulden]

pow needs to be Math.pow

Thank's Steve, you are very helpful.

[MickinMoulden]

and .... you've made vars T and RH strings not numeric.

Multiplication and division in the formula will appear to work correctly, but subtraction and addition will not !

Thanks for the information. But more importantly, how do I make vars T and RH numeric, when I thought ="5" would be.
Also, you say subtraction and addition will not work corectly. Is it now broken? I'll try reading more on that nasty JavaScript in the tutorials and teach them how to add and stuff.

[MickinMoulden]

pow needs to be Math.pow

Thanks again Steve, all I did was add that and it works. Cheers mate.
Now I will add the background colours to the warning message. I also made changes to which temperature it could read from and to what value they should be.
Ideally I would like the FDI formula, but the ones I could find I didn't know how to impliment

[gemini06720]

Michael, I certainly do not want to stop you with your project...

The CBI (Chandler Burning Index) uses six expressions/terms: 'Nil','Low','Moderate','High','Very High','Extreme' using the following:

Code: Select all

$cbiindex > "97.5" // Extreme
$cbiindex >=  "90" // Very High
$cbiindex >=  "75" // High
$cbiindex >=  "50" // Moderate
$cbiindex <   "50" // Low
$cbiindex <=   "0" // None

You might also be interested in this software: FWI Calc. Once setup, it produces some very accurate results which can be incorporated into a Web page (I have been using for a couple of years).

[yv1hx]

...You might also be interested in this software: FWI Calc. Once setup, it produces some very accurate results which can be incorporated into a Web page (I have been using for a couple of years).

I agree 100% with gemini06720.

I been running FWCalc since past year without any complaints, please have a look at:

http://met.ivic.gob.ve/red/Cabimas/FWICalc/fwistats.htm (Statistics)
http://met.ivic.gob.ve/red/Cabimas/FWICalc/fwi.htm (Graphs)

Note:
Texts are in Spanish language, because the intended audience is local only, however, should be understood beyond the language barrier... Sorry for the inconveniences.

[pekkie]

Good evening everyone. you want to ask for help. I have configured the FwiCalc software and I have sent the data online the problem and not showing. how can i do to fix it? I as a weather software have Cumulus. the site and this:
http://www.meteobrianza.net/wxcalcul.php