WRF-HAILCAST Hail Forecasting System Improvements
Several improvements have been made to WRF-HAILCAST since the 2014 HWT. Constant initial hailstone embryo sizes are now used instead of retrieving initial embryo sizes from the microphysical parameterization graupel size distribution, notably reducing the sensitivity of WRF-HAILCAST to the microphysical parameterization; this improvement was part of the WRF v3.6.1 release. The required processing time was also significantly reduced (included in the v3.7 release). Forecasts from the 2014 HWT during a selected time period were rerun using these WRF-HAILCAST improvements, and verification statistics from these forecasts will also be presented. Finally, results from sensitivity tests will be shown that evaluate the effects of perturbations in updraft strength on the forecast hail diameter.