HAFS-Basin: Development of a Multi-Storm Configuration to Improve Tropical Cyclone Forecasts

The Hurricane Analysis and Forecast System (HAFS) is the tropical cyclone (TC) application of NOAA’s Unified Forecast System (UFS) that is now operational at the National Oceanic and Atmospheric Administration (NOAA). The operational configuration of HAFS includes a single moving (i.e., storm-following) nested domain, similar to the longtime Hurricane Weather Research and Forecasting (HWRF) model. This work focuses on the development of a non-storm-centric configuration of HAFS, tentatively called “HAFS-Basin”, that will support TC research and could be implemented into operations. HAFS-Basin includes multiple moving nests that produce high-resolution forecasts for more than one TC in one or more ocean basins, all interacting in a coarser resolution, fixed outer atmospheric domain coupled with an ocean model. Previous work (e.g., Basin-scale HWRF; HWRF-B) demonstrated the benefit of simulating interactions between multiple TCs at high-resolution using moving nests. Accordingly, HWRF-B serves as motivation and guidance for HAFS-Basin activities. Ongoing HAFS-Basin developments include production of optimal initial conditions for each moving nest, including those that are near the boundary of the parent domain. HAFS-Basin will also facilitate exploration of long-term priorities, including the expansion of HAFS data assimilation beyond the TC itself (e.g., synoptic-scale environment) and moving nests within a global configuration of HAFS.