Energy Release Component/Burning Index Charts
Energy Release Component - An indicator of how much potential energy is available to be released per unit area in the flaming front. The energy release component fluctuates daily based on the fuel moistures. ERC does not include wind in any part of the index calculation, and is heavily weighted to large fuel moistures. Due to this fact, the ERC index shows the cumulative effect of weather over time on large fuels. The drying of large fuels result in an increasing ERC, while an ERC decrease indicates a net gain in large fuel moisture. Large fuel moistures are a key factor in fire intensity, high intensity fires having a high resistance to control.
The Burning Index (BI) is a combination of ERC and Spread Component (SC). ERC does not include wind in the index calculation, and is highly weighted to large fuel moistures. SC is very sensitive to wind and is weighted to fine fuel moistures. The BI can fluctuate fairly dramatically from day to day, but does have a seasonal trend. Fires can occur at a BI of zero, but would have little spread potential as long as conditions on the fire were similar to conditions at the weather station, where the index value was computed from.
The horizontal lines represent the fire danger levels.
Originally there were 6 Fire Danger Rating Areas. Four of the areas, Pumice, Fremont, Basin & Westside were combined to make the Central Area. ERC Charts of the original areas. Map of Fire Danger Rating Areas.