Regional and Mesoscale Meteorology Branch

Improvements to the National Hurricane Center (NHC) Gridded Tropical Cyclone forecast advisory Message (GTCM) surface wind model

Improvements to NHC’s GTCM model were developed and made available to NHC for operational implementation for the 2026 Hurricane Season. The GTCM provides a 2-D surface wind field at hourly intervals using input from the NHC official forecast, which is a text product that includes the tropical cyclone (TC) center location, maximum wind and radii of 34, 50 and 64 kt winds out to 5 days. Improvements include a new wind gust parameterization, dynamic grid adjustment to account for large TCs, and a better method for fitting the NHC forecast input to the parametric vortex used by the GTCM. The GTCM is used as guidance by the National Weather Service for TC watches and warning and their gridded forecast products.  The figure below shows an example of a cumulative swath of sustained wind and wind gusts for the landfall of Hurricane Helene (2024). (POCs: M. DeMaria, A. Brammer, Mark.DeMaria@colostate.edu, Alan.Brammer@colostate.edu, Funding NWS/STI and NOAA/JTTI).

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Posted on: February 20, 2026