ECMWF took the ensemble version of the Artificial Intelligence Forecasting System (AIFS) into operations on 1 July 2025, to run side by side with its traditional physics-based Integrated Forecasting System (IFS). The ensemble version, called AIFS-ENS, is a collection of 51 different forecasts with slight variations at any given time to provide the full range of possible scenarios. A first operational version which runs a deterministic forecast, called AIFS Single, was released at the end of February.
The new ensemble model outperforms state-of-the-art physics-based models for many measures, including surface temperature, with gains of up to 20%, but it runs at a lower resolution of 31 km compared to the physics-based ensemble system, which runs at 9 km. More information on the AIFS ENS can be found on our website: https://www.ecmwf.int/en/about/media-centre/news/2025/ecmwfs-ensemble-ai-forecasts-become-operational. A detailed article on the AIFS ENS is planned for the next Newsletter.