An Overview of Tropical Cyclones in the FV3GFS Retrospectives

NOAA’s Global Forecast System (GFS) spectral model will be replaced by the FV3 dynamical core in 2019 as a part of the Next Generation Global Prediction System (NGGPS) Project. This is the first step in the transition of the entire NCEP model suite over to the FV3 dynamical core as part of the Unified Forecast System (UFS). While most of the operational GFS physics will be retained in the transition to the FV3GFS, the dynamical core will be replaced and the model will be updated with GFDL microphysics. As such, it is critical to evaluate the performance of the FV3 dynamical core for various case studies and to compare it to the current operational GFS to make sure that there is no degradation in model skill. Of particular interest are high-impact landfalling tropical systems that have impacted the Southern Hemisphere, islands in the western Pacific Ocean, and the southern and eastern United States.

The Model Evaluation Group (MEG) of the Environmental Modeling Center (EMC) carefully selected tropical case studies from 2015 to 2017 in order to assess the differences between the operational GFS and the FV3GFS in forecasts of track, intensity (both winds and minimum pressure), quantitative precipitation (QPF), and storm intensification. The MEG focused on hurricanes that significantly impacted the United States including Joaquin, Harvey, Irma, Maria, Nate, and Matthew. In addition, the analysis included western Pacific typhoons Soudelor and Noru, and Southern Hemisphere cyclones Winston, Amos, and Gita. The ultimate purpose of this evaluation is to help prepare the forecasting community to use the FV3GFS for tropical cyclone forecasting once the model officially becomes operational in 2019.