Although a future single-core ensemble system will leverage the FV3 dynamic core, HRRRE provides a real-time, ARW-based proving ground for testing various techniques to improve ensemble performance. In addition to initial condition perturbations that target random error, HRRRE has been using a stochastic parameter perturbation approach to address model error since late spring 2019.
Here we compare forecasts of heavy rainfall from the HREFv2 and HRRRE ensembles over the eastern United States during Jun-Aug 2019. Various metrics are used to evaluate model biases, spatial representation of precipitation, and the reliability and sharpness of probabilistic forecasts. These early results indicate generally useful guidance from both systems, in spite of a number of deficiencies inherent in forecasts of localized heavy rainfall. By several measures, HRRRE achieves performance comparable to that of HREF, suggesting potential for accurate representation of atmospheric uncertainty using approaches other than a multi-core, multi-physics ensemble.