Improving Lightning Density Guidance with Calibrated Probabilities from Ensemble Model Output

Lightning-ignited wildfires are responsible for the majority of acreage burned across the United States. Thunderstorm and lightning guidance are imperative to fire weather forecasts, which are used by wildland fire managers when making decisions about resource allocation and suppression tactics. The Storm Prediction Center (SPC) Short Range Ensemble Forecast (SREF) calibrated thunder forecast guidance currently provides probabilistic forecasts on different temporal scales detailing the probability of one or more and 100 or more cloud-to-ground (CG) lightning flashes in a 40-km grid box. Verification of the SPC SREF calibrated probabilistic thunder guidance for one or more CG lightning flashes demonstrates reliable and accurate forecasts and verifies better overall than forecasts for 100 or more CG lightning flashes. Decision support services, including wildland fire management, often need more precise information on the amount of expected lightning than that offered by the one or more CG lightning flash guidance. In this study, the SPC SREF calibrated thunder approach is refined to improve lightning density guidance, including examination of other variables to enhance the predictive skill. Forecast probabilities of CG lightning that exceed different density thresholds ranging from 10 to 30 CG lightning flashes in 1- and 3-hour periods (out to an 87-hour forecast) are generated and results are compared to existing lightning density forecasts.