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

Canonical page: https://technooptimist.io/stories/noaa-upgrades-aigfs-to-v1-1-to-sharpen-hurricane-intensity-and-rainfall-c559bd53
Date: 27 Jul 2026
About: [NOAA](https://technooptimist.io/companies/noaa.md) · [AIGFS](https://technooptimist.io/ai/aigfs.md)
Original source: https://www.weather.gov/media/notification/pdf_2026/scn26-68_AIGFS_v1.1.pdf

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.

## Key facts

- 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.

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