Evaluation of WRF-HAILCAST Hail Model Forecasts across Environmental Regimes

The WRF-HAILCAST hail forecasting system is a one-dimensional hail growth model integrated into the WRF-ARW model and designed to predict hail size at the ground. During the past four NOAA Hazardous Weather Testbed Spring Forecasting Experiments (2014-2017), WRF-HAILCAST was run within the NSSL WRF-ARW, the CAPS Storm-Scale Ensemble Forecast (SSEF), and the NCAR WRF ensembles. Object-based and objective verification statistics will be presented from all four years of forecasts, with a discussion of how improvements between years are related to improvements in the physics of the WRF-HAILCAST model. Model forecasts will also be compared to Day 1 convective outlooks issued by the Storm Prediction Center. Verification statistics will be subdivided by environmental CAPE and shear regimes to determine effectiveness of the model across regimes. Sample hail trajectories from storms within the different regimes will be presented to examine model performance.