A Multi-Storm Configuration of the Hurricane Analysis and Forecast System (HAFS)

The Hurricane Analysis and Forecast System (HAFS) is the tropical cyclone (TC) application of NOAA’s Unified Forecast System (UFS) and the flagship operational hurricane model at National Oceanic and Atmospheric Administration (NOAA). In operations, HAFS employs a storm-centric approach, meaning only a single TC is tracked with a high-resolution storm-following nest per forecast integration. Previous work demonstrates that a multi-storm approach (i.e., multiple storm-following nests) leads to significant TC forecast improvements. As such, a new multi-storm configuration of HAFS (called “HAFS-M”) has been developed and is being evaluated to support TC research and, potentially, to improve operations. In HAFS-M, multiple moving nests produce atmosphere-ocean-coupled high-resolution forecasts for more than one TC in a fixed parent domain that spans one or more ocean basins, facilitating the exploration of storm-storm and multi-scale interactions on a level that cannot be accomplished with storm-centric configurations. Furthermore, HAFS-M motivates data assimilation research and advancements, including exploration of how to optimally assimilate observations into several TCs at once and how to maximize the impact of new and existing observing systems. All of this work is being performed within the HAFS code repository, meaning many of the advancements in HAFS-M will be available to transition to future operational versions of HAFS.