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HAFS Forecasts Contribute to More Effective Emergency Response

Author: Dr. Zhan Zhang, Hurricane Modelling team lead at NCEP/EMC, co-lead of NOAA’s Unified Forecast System (UFS) research and member of the operation (R2O) Hurricane Application Team

Early and accurate warnings from NOAA’s National Hurricane Center (NHC), are integral to protecting any community threatened by hurricanes and tropical storms. This is the purpose of NOAA’s newest hurricane model, the Hurricane Analysis and Forecast System (HAFS), which significantly improves the accuracy of forecasts and further supports community action in preparation of such severe weather events.

Hurricane Analysis and Forecast System (HAFS) is NOAA’s next-generation operational modeling system for significantly advancing Tropical Cyclone (TC) forecast guidance in all global ocean basins. As a result of multi-year collaboration among NOAA Line Offices, research, and operational communities, on June 27, 2023, two configurations of HAFS version 1, HFSA and HFSB, were implemented into operations at the National Weather Service (NWS) National Centers for Environmental Prediction (NCEP).

HAFS was developed using NOAA’s community-based Unified Forecast System (UFS) framework which allows NCEP to consolidate and simplify its production suite of forecasting models from many independent systems. Since HAFS shares the same UFS code base, it is able to take advantage of all the latest model dynamics and physics developments, with special emphasis on cloud-resolving scale TC applications.  

HAFS is the first major UFS-based regional operational system, incorporating advanced features like atmosphere-ocean-wave coupling, high-resolution storm-following nests at cloud-permitting scales, sophisticated vortex initialization, inner-core data assimilation, and model physics specifically tailored for TC applications. As a community model, HAFS enables researchers to work with the operational model configurations, facilitating the transition of new research findings into operational use and supporting a continuous cycle of research-to-operations-to-research (R2O2R), supported by the Hurricane Forecast Improvement Program (HFIP).

Above: Animations from operational HAFSv2 (Hurricane HeleneMilton). Animations show perfect HAFS track forecasts for Hurricanes Helene and Milton, the two US landfalling hurricanes that significantly impacted the US coast and inland areas in 2024 hurricane season.

Above: Example of rainfall swath from HAFS (Helene). Model comparison of precipitation compared to the CCPA (Climatology-Calibrated Precipitation Analysis)

Above: Example of wind field and radar reflectivity comparisons with tail Doppler radar (TDR) observations (Milton). The HAFS model is able to accurately reproduce wind speed fields and radar reflectivity patterns, such as secondary eyewall structure, compared to the observations.