Wednesday, 14 November 2001: 4:20 PM
The 10 Day Fire Potential Assessment
Monthly and seasonal assessments of potential fire severity (based on climatology, fire occurrence records, 30-day and 90-day weather forecasts) have become widely used over the past few years in long-range planning and resource allocation for wild and prescribed fires. In the short term, the National Fire Danger Rating System (NFDRS), based on 24-hour weather trends, is used to determine the next day’s fire resource staffing level. However, no information is currently available in the mid-term (10-day) time frame, leaving fire managers to determine fire risks based upon very generalized weather forecasts. In addressing this need, the Predictive Services staff at the Northwest Interagency Coordination Center has developed a method for assessing potential fire severity in 10-day increments throughout the summer fire season. Daily temperature and relative humidity forecasts for a selected number of Remote Automatic Weather Stations (RAWS) have been developed as input into the NFDRS calculator of the Fire Family Plus computer program. These daily forecasts were derived through a regression analysis technique using model grid point data from the ETA and AVN models with an MRF extension to 10 days. NFDRS outputs from the calculator include: 1,000-hour Fuel Moisture, the Energy Release Component, and Live Fuel Moisture. These projected 10-day values are compared to the mean for the date and to critical thresholds determined by the historical occurrence of large wildland fires. Weather patterns throughout the 10-day period are also evaluated to identify critical fire weather days (i.e. strong wind in combination with low relative humidity, the presence of lightning or high Haines Index days) that may significantly increase the threat of large wildland fires that present safety concerns for both firefighters and the general public.