Fire Weather Index (FWI):
The FWI is a measurement of various components to predict the possibility of wildfires. There are two standard measurements for the FWI. The Haines Index and the Chandler Burning Index. Both are explained below.

The Haines Index:
The Haines Index is the sum of a stability term and a moisture term. The sum provides an indication of the potential for the rate of spread (ROS) of a fire on a given day. A Haines Index of 2-3 = a very low ROS, 4 = low ROS, 5=moderate ROS, and 6 = high ROS. The National Weather Service uses the Lower Atmospheric Severity Index (LASI) to quantify the potential for forest fire growth.

For more in-depth information click HERE.

LOW ELEVATION Stability Term
(T950-T850)
  • ≤3°C
  • 4 to 7°C
  • ≥8°C
 Moisture Term
(T850-Td850)
  • ≤5°C
  • 6 to 9°C
  • ≥10°C
MID ELEVATION Stability Term
(T850-T700)
  • ≤5°C
  • 6 to 10°C
  • ≥11°C
 Moisture Term
(T850-Td850)
  • ≤5°C
  • 6 to 12°C
  • ≥13°C
HIGH ELEVATION Stability Term
(T700-T500)
  • 17° C or less
  • 18 to 21° C
  • 22° C or gtr.
 Moisture Term
(T700-Td700)
  • 14° C or less
  • 15 to 20° C
  • 21° C or gtr

The Chandler Burning Index:
The Chandler Burning Index (CBI) uses the air temperature and relative humidity to calculate a numerical index of fire danger. That number is then equated to the Fire Danger severity of either extreme, very high, high, moderate, or low. It's based solely on weather conditions, with no adjustment for fuel moisture. Here on the K3JAE Weather site, the CBI is calculated from the current weather conditions and reflects the current calculated fire danger. The National Weather Service calculates a 30 day Chandler Burning Index based on forecasted weather conditions for the month.

For more in-depth information click HERE.