AIFS

ECMWF's machine-learning global weather model, run operationally beside its physics-based system since 2025; weights published openly.

The Artificial Intelligence Forecasting System is the European Centre for Medium-Range Weather Forecasts' data-driven weather model. It uses a graph neural network encoder and decoder with a transformer processor, trained first on ERA5 reanalysis for 1979 to 2022 and then fine-tuned on ECMWF's own operational analyses. It runs alongside, not instead of, the physics-based Integrated Forecasting System, which still supplies the initial conditions.

It forecasts upper-air and surface variables, including 100 m winds, solar radiation, cloud cover, snowfall, soil moisture and tropical cyclone tracks, at about 28 to 31 km grid spacing and 13 pressure levels, in 6-hour steps. ECMWF reports that it beats its physics-based models on many scores and uses roughly a thousand times less energy per forecast.

The weights of AIFS Single v1.0 are published on Hugging Face under CC BY 4.0, with Apache-2.0 notebooks for running them. The model was trained with Anemoi, ECMWF's open framework for machine-learned forecasting.

Operational: AIFS Single since 25 February 2025 and the 51-member AIFS ENS since 1 July 2025, both with ECMWF's round-the-clock support.