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Predictive Services

Fire danger ratings describe conditions that reflect the potential, over a large area, for a fire to ignite, spread, and require suppression action. Fire danger rating compares past, current, and forecasted weather. Fire danger rating is a tool designed to aid fire managers in making day-to-day decisions on preparedness, suppression readiness, prevention activities, and dispatch level needs.

The energy release component (ERC) is a calculated output of the national fire danger rating system (NFDRS). The ERC is a number related to the available energy (BTU) per unit area (square foot) within the flaming front at the head of a fire. The ERC is considered a composite fuel moisture index as it reflects the contribution of all live and dead fuels to potential fire intensity. As live fuels cure and dead fuels dry, the ERC will increase and can be described as a build-up index. The ERC has memory. Each daily calculation considers the past 7 days in calculating the new number. Daily variations of the ERC are relatively small as wind is not part of the calculation.

The ERC relates well to the condition of the fuels. Fire managers and planners have found that the ERC can be used as a decision tool to prepare for an approaching fire season or it can be used as a tool for daily staffing when used in combination with other NFDRS components such as 100-hr fuel moisture or the burning index (bi). Tracking the ERC and other NFDRS components through the season and on a daily basis will increase the situational awareness of wildland firefighters.


ERC Seasonal Graphs by PSA

Fuels are always gaining or losing moisture. Dead fuel moisture responds solely to ambient environmental conditions and is critical in determining fire potential. Dead fuel moistures are classified by time lag and is proportional to its diameter and is loosely defined as the time is takes a fuel particle to reach 2/3's of its way to equilibrium with its local environment. Dead fuels in the national fire danger rating system fall into four classes.

• 1-hour (less than ¼" diameter): fine, flashy fuels that respond quickly to weather changes.

• 10-hour (1/4"-1" diameter): lower 10-hour fuel moisture provides guidance toward an earlier and later burn period. When forecast 10-hour fuel moisture percentiles are at or the below the 25th percentile, that is a good indicator of poor overnight relative humidity recoveries and increased availability of cured grasses.

• 100-hour fuel (1"-3" diameter): provides guidance toward availability of brush/timber litter fuel when stations are at or below the 25th percentile.

• 1000-hour fuel (3"-8" diameter): low 1000-hr fuel moisture is an indicator of drought. As 1000-hour fuel moisture decreases, the intensity toward the mop-up phase increases to lower escape potential.

Monitoring live fuel moisture is important to track and identify when canopy fuel is becoming more receptive to burning, increasing the resistance to control of wildfire. The predictive services department conducts monthly live fuel sampling in high risk fuel species across the state. Results are posted on the national live fuel sampling database.

Weather plays a vital role in the fire environment toward fire potential and fire behavior. Firefighters and fire management staff are responsible for keeping up with current and forecast weather conditions. The predicative services department maintains an important partnership with the National Weather Service by collaborating and communicating burning conditions.

Weekly and Seasonal Fire Potential Outlooks are designed to maintain awareness about current and future burning conditions.

These tools are designed for firefighters to review and maintain situational awareness toward historical burning conditions by predictive service area.


Critical Thresholds by PSA

Fire behavior is the site specific, description of an existing fire in a given time and space. Fire behavior describes the movement (rate of area increase), intensity (flame length), and indicators of rapid combustion (spotting, crowning, and fire whirls) of that fire. It is expressed as real time or predicted conditions for ongoing fires. For example, the flame length is 4 to 5 feet.

Drought implies an increased availability of dead and live fuels that will contribute to combustion. Increased fuel loading will increase fire intensity, increase the rate of spread and generally increase a wildfire's resistance to control. These tools are designed to monitor changes in precipitation deficits and identify emerging dryness in the state.

Gain a wider situational awareness with the tools listed below through the National Interagency Coordination Center, National Interagency Fire Center and the Geographic Area Coordination Centers.

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Predictive Services