Evaluation of HAILCAST during NOAA/Hazardous Weather Testbed Spring Forecasting Experiments using Multiple Verification Metrics

HAILCAST is a one-dimensional hail growth model currently integrated into the WRF-ARW model and designed to predict hail size on a convective scale. During the past four NOAA Hazardous Weather Testbed (HWT) Spring Forecasting Experiments (2014-2017), HAILCAST was run within the NSSL WRF-ARW Ensemble, the CAPS Storm-Scale Ensemble Forecast (SSEF), the Community Leveraged Unified Ensemble (CLUE), and the NCAR WRF ensemble. Objective verification using the Maximum Expected Size of Hail (MESH) product was conducted using both object-based and traditional grid-based verification. Results will be presented from all four years of forecasts, and improvements between years related to improvements in the physics of the HAILCAST model. HAILCAST forecasts will also be compared to hail size/storm surrogate forecasts using updraft helicity, maximum column updraft speed, and column-integrated graupel, as well as Day 1 convective outlooks issued by the Storm Prediction Center. Results from different verification methods will be compared, and recommendations for future hail forecast verification methods presented.