An Investigation of Tropical Cyclogenesis Forecast Performance with the Basin-Scale HAFS

This study examines and evaluates the performance of an experimental version of Hurricane Analysis and Forecast System (HAFS) in the prediction of tropical cyclogenesis. HAFS is the latest operational hurricane model, launched in 2023 as part of the NOAA’s Hurricane Forecast Improvement Program (HFIP) development. The recent development of Basin-Scale or Multi-Storm HAFS (HAFS-M) has enabled the capability of high-resolution predictions for multiple storms within the same forecast integration. In this study, moving nests will be assigned to multiple areas of interest (i.e., pre-genesis) based on the tropical weather outlook produced by the National Hurricane Center (NHC). The updated HAFS-M domain covers both the North Atlantic basin and the eastern North Pacific basin, which are the main areas of forecast responsibility for NHC. The fixed outer domain size is about 125° by 60° with a 6-km resolution and the moving nests are about 12° by 12° with 2-km resolution. On the other hand, the operational HAFS utilizes one moving nest with a 80° by 80° outer domain, both centered on a single storm of interest. The operational HAFS predicts each storm independently when there are multiple storms of interest, while HAFS-M is capable of predicting co-occurring storms within one run. To evaluate the impact of multiple moving nests on tropical cyclone genesis predictions, the HAFS-M performance was examined and compared with various HAFS versions that were configured with a single moving nest or no moving nest.