A Progress Report on the Development of the High-Resolution Rapid Refresh Ensemble

Abstract The High-Resolution Rapid Refresh Ensemble (HRRRE) is a 36-member ensemble analysis system with 9 forecast members that utilizes the Advanced Research version of Weather and Forecasting (ARW-WRF) dynamic core physics suite from operational Refresh/High-Resolution deterministic modeling system. A goal HRRRE development sufficient spread among members, comparable in magnitude to random error mean, represent range possible future atmospheric states. member diversity has traditionally been obtained by perturbing initial lateral boundary conditions each member, but recent focused on implementing stochastic approaches generate additional spread. These techniques were tested retrospective experiments May 2019 Hazardous Testbed Spring Experiment (HWT-SE). Results show 6%–25% increase 2-m temperature, mixing ratio, 10-m wind speed when parameter perturbations are used (HRRRE-SPP). Case studies HWT-SE demonstrate HRRRE-SPP performed similar or better than Forecast system, 2 (HREFv2), nonstochastic HRRRE. However, subjective evaluations provided forecasters indicated overall, predicted lower probabilities severe weather (using updraft helicity as proxy) compared HREFv2. statistical performance HREFv2 summer convective season supports this claim, also demonstrates two systems have reliability for prediction using helicity.