NOAA upgrades AIGFS to v1.1 to sharpen hurricane intensity and rainfall forecasts

NOAA/AIGFS

The National Weather Service switched AIGFS to version 1.1 from the 12:00 UTC run on 27 July 2026. The changes target the model's known weak spots: underpowered hurricanes, rainfall, and forecasts that blur at longer lead times.

• Loss function changed from grid-point squared error to a spherical-harmonic loss, using wind speed and direction.
• Fine-tuned on four years of NOAA's Global Data Assimilation System analyses.
• Trained autoregressively out to 72 hours, so the model learns from its own multi-step forecasts.
• Developed by NOAA's Environmental Modeling Center with NOAA research labs and EPIC.