How Well Does an FV3‐based Model Predict Precipitation at a Convection‐Allowing Resolution? Results from CAPS Forecasts for the 2018 NOAA Hazardous Weather Testbed with Different Physics Combinations

The Geophysical Fluid Dynamics Laboratory (GFDL) Finite-Volume Cubed-Sphere (FV3) numerical forecast model was chosen in late 2016 by the National Weather Service (NWS) to serve as the dynamic core of the Next-Generation Global Prediction System (NGGPS). The operational Global Forecasting System (GFS) physics suite implemented in FV3, however, was not necessarily suitable for convective-scale prediction. We implemented several advanced physics schemes from the Weather Research and Forecasting (WRF) model within FV3 and ran 10 forecasts with combinations of five planetary boundary layer and two microphysics (MP) schemes, with an similar to 3.5-km convection-allowing grid two-way nested within am similar to 13-km grid spacing global grid during the 2018 Spring Forecasting Experiment at National Oceanic and Atmospheric Administration (NOAA)'s Hazardous Weather Testbed. Objective verification results show that the Thompson MP scheme slightly outperforms the National Severe Storms Laboratory MP scheme in precipitation forecast skill, while no planetary boundary layer scheme clearly stands out. The skill of FV3 is similar to that of the more-established WRF at a similar resolution. These results establish the viability of the FV3 dynamic core for convective-scale forecasting as part of the single-core unification of the NWS modeling suite. Plain Language Summary In this paper we examine how well the Finite-Volume Cubed-Sphere (FV3) model predicts precipitation over the Contiguous United States (CONUS) when run at a resolution sufficient to explicitly predict convective storms. FV3 was chosen to replace the operational Global Forecast System (GFS) by the National Weather Services (NWS) in late 2016, but its performance for convective-scale regional forecasting was previously untested. The physical parameterization schemes available in FV3 were mostly from GFS and not necessarily suitable for convective-scale predictions. We implemented several advanced physics schemes taken from a more established and most widely used convective-scale model, the Weather Research and Forecasting (WRF) model, into FV3, including schemes for treating turbulence exchanges in atmospheric boundary layer and those for representing cloud and precipitation processes (microphysics). We ran 10 forecasts each day using different combinations of the physics schemes to evaluate their performance in FV3 as part of the 2018 National Oceanic and Atmospheric Administration (NOAA) Hazardous Weather Testbed Spring Forecasting Experiment. With these advanced schemes, FV3 is shown to be capable of predicting precipitation with skill comparable to WRF. The precipitation forecast is somewhat sensitive to the microphysics schemes used, but not particularly sensitive to the atmospheric boundary layer scheme. Our study shows that the newly selected FV3 model, when equipped with appropriate physics parameterization schemes, can serve as the foundation for the next-generation regional forecasting models of the NWS.