The Hurricane Forecast Improvement Project: Basin-Scale HWRF Performance in 2018

“Stream 2” is a major component of NOAA’s Hurricane Forecast Improvement Project (HFIP) that supports real-time demonstrations of numerical weather prediction models. The purpose of HFIP Stream 2 is to improve hurricane forecast performance by applying advanced science and technology with the assumption that the computational resources required for these demonstrations will become available in operations. In fact, all major research transitions into the operational Hurricane Weather Research and Forecasting (HWRF) model have resulted from HFIP Stream 2 activity. For the 2018 hurricane season, an advanced version of the HWRF system, called the Basin-scale HWRF (HWRF-B), was a real-time HFIP Stream 2 project that ran on the NOAA Jet supercomputer. The performance of HWRF-B forecasts in 2018, including landfalling major hurricanes (e.g., Florence and Michael), were directly compared with HWRF and other operational NOAA models. Overall, HWRF-B showed significant improvement over the operational HWRF for forecasts with multiple active tropical cyclones in the Atlantic and eastern Pacific basins. For instance, HWRF-B forecasts for Hurricane Isaac were much improved compared with HWRF, in part due to multiple high-resolution moving nests that captured realistic multi-storm interactions between Hurricanes Florence, Helene, and Isaac. HWRF-B tended to produce an unfavorable environment near Isaac, with higher vertical wind shear and lower mid-level moisture that contributed to its dissipation. The paradigm of multiple high-resolution moving nests is vital to the future of NOAA hurricane forecasts, and these nests are currently a high priority development for the FV3GFS.