Sandaysoft

There has been talk in various posts about different fire danger indices.

I have just finish work on a Javascript Calculator for the NSW Fire Danger Index (FDI) and thought others might be interested.

I have been a volunteer firefighter for 30 years and find this stuff very interesting as well as helpful operationally.

The source of my information can be found at: http://www.firebreak.com.au/bkdi_df.html

For this to work you need the following:
- Byram-Keetch Drought Index (BKDI) (mm) - this is the measure of fine fuels available to a fire;
- The Drought Factor (DF) - Calculated from the BKDI, "Days Since Rain" and "Rain in the past 24 hours";
- Current Temperature;
- Current Humidity;
- Current (Average) wind speed.

Note: I have to calculate the BKDI in an excel spreadsheet because it is a cumulative number. Your can just assume a BKDI of 100 or to simplify the process even further a DF of 10. Anything greater has little effect on the final rating.

My script is as follows:
<script type="text/javascript" language="Javascript">

var BKDI = 17;
var DF = 10;
var FDI = 0;
var Rating = "LOW/MODERATE";

//Calculate Drought Factor

DF = Math.round(((0.191*(BKDI+104)*(<#ConsecutiveDryDays>+1)^1.5)/(3.52*(<#ConsecutiveDryDays>+1)^1.5+<#r24hour>-1)));

if (DF>10) {DF = 10};

//Calculate Fire Danger Rating

FDI = Math.round(1.275*(DF^0.987)*Math.exp((<#temp>/29.5858)-(<#hum>/28.9855)+(<#wspeed>/42.735)));

if (FDI>11) {Rating = "HIGH"};
if (FDI>24) {Rating = "VERY HIGH"};
if (FDI>49) {Rating = "SEVERE"};
if (FDI>75) {Rating = "EXTREME"};
if (FDI>99) {Rating = "CATASTROPHIC"};

</script>

I used the following script to display the results on the page:
<tr class="td_fire_data">
<td>BKDI</td>
<td>
<script language="JavaScript">
document.write(BKDI);
</script>
</td>
<td>Drought Factor</td>
<td>
<script language="JavaScript">
document.write(DF);
</script>
</td>
</tr>
<tr class="td_fire_data">
<td>Fire Danger Index (FDI)</td>
<td>
<script language="JavaScript">
document.write(FDI);
</script>
</td>
<td>Rating</td>
<td>
<script language="JavaScript">
document.write(Rating);
</script>
</td>
</tr>

I have inserted this into the indexT.htm file.

An example of what it looks like can be found here: http://www.rhumbline.com.au/weather/index.htm