Recently, forecasters at the Storm Prediction Center, in Norman, OK, have begun using short range ensemble forecast (SREF) output as guidance for their national fire weather outlooks. The SPC forecasters outlook critical and extremely critical fire weather areas, for a 24-48 hour time period. These areas are evaluated by inspecting grids of maximum temperature, minimum RH values, sustained surface winds, in addition to antecedent drought conditions. Dry lightning is also forecasted and is considered to be a critical/extremely critical fire weather outlook area.

The use of SREF output enhances the forecast process by highlighting the likelihood of key fire weather parameters reaching critical values. Forecasters use GEMPAK scripts which allow them to display data from the NCEP 15 member (SREF). The NCEP SREF contains output from the Eta, the Eta with the Kain-Fritsch (KF) convective parameterization, and the regional spectral model (RSM). There is a control run for each model, in addition to four initial conditions. In this way, statistical characteristics of model solutions can be used in creating the fire weather outlooks. Forecasters can display a variety of statistical fields including probability, median, mean, max/min, standard deviation, and “spaghetti” charts.

SPC fire weather outlooks are verified by the Fosberg Fire Weather Index (FWI). The Fosberg FWI is calculated using temperature, RH, and wind thresholds. The ensemble output has forecast Fosberg FWI fields. Greater confidence in higher Fosberg FWI values is accomplished quickly and easily by using data from the NCEP SREF.

Short range ensembles will become a standard tool in operational forecasts in the future. The SPC is already implementing this latest technology in creation of its fire weather outlooks. It is hoped that this new way of looking at short range solutions will result in improved forecast products.