Exploring Convection-Allowing Model Evaluation Strategies for Severe Local Storms Using the Finite-Volume Cubed-Sphere (FV3) Model Core Weather and Forecasting

Verification methods for convection-allowing models (CAMs) should consider the finescale spatial and temporal detail provided by CAMs, and including both neighborhood and object-based methods can account for displaced features that may still provide useful information. This work explores both contingency table–based verification techniques and object-based verification techniques as they relate to forecasts of severe convection. Two key fields in severe weather forecasting are investigated: updraft helicity (UH) and simulated composite reflectivity. UH is used to generate severe weather probabilities called surrogate severe fields, which have two tunable parameters: the UH threshold and the smoothing level. Probabilities computed using the UH threshold and smoothing level that give the best area under the receiver operating curve result in very high probabilities, while optimizing the parameters based on the Brier score reliability component results in much lower probabilities. Subjective ratings from participants in the 2018 NOAA Hazardous Weather Testbed Spring Forecasting Experiment (SFE) provide a complementary evaluation source. This work compares the verification methodologies in the context of three CAMs using the Finite-Volume Cubed-Sphere Dynamical Core (FV3), which will be the foundation of the U.S. Unified Forecast System (UFS). Three agencies ran FV3-based CAMs during the five-week 2018 SFE. These FV3-based CAMs are verified alongside a current operational CAM, the High-Resolution Rapid Refresh version 3 (HRRRv3). The HRRR is planned to eventually use the FV3 dynamical core as part of the UFS; as such evaluations relative to current HRRR configurations are imperative to maintaining high forecast quality and informing future implementation decisions. 2021 2021-08-02T00:00:00Z Grant no. NA16OAR4320115 Grant no. NA19OAR4590141 Grant no. NA17OAR4590186 Grant no. NA16NWS4680002 Mesoscale forecasting Numerical weather prediction/forecasting Operational forecasting Model comparison Model evaluation/performance NWS (National Weather Service) NCEP (National Centers for Environmental Prediction) OAR (Oceanic and Atmospheric Research) GFDL (Geophysical Fluid Dynamics Laboratory) ESRL (Earth System Research Laboratory) NSSL (National Severe Storms Laboratory) CIMMS (Cooperative Institute for Mesoscale Meteorological Studies) Submitted https://doi.org/10.1175/WAF-D-20-0090.1 Other 1948