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arXiv · 2509.18994

An update to ECMWF's machine-learned weather forecast model AIFS

Gabriel Moldovan·Ewan Pinnington·Ana Prieto Nemesio·Simon Lang·Zied Ben Bouallègue·Jesper Dramsch·Mihai Alexe·Mario Santa Cruz·Sara Hahner·Harrison Cook·Helen Theissen·Mariana Clare·Cathal O'Brien·Jan Polster·Linus Magnusson·Gert Mertes·Florian Pinault·Baudouin Raoult·Patricia de Rosnay·Richard Forbes·Matthew Chantry
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Abstract

We present an update to ECMWF's machine-learned weather forecasting model AIFS Single with several key improvements. The model now incorporates physical consistency constraints through bounding layers, an updated training schedule, and an expanded set of variables. The physical constraints substantially improve precipitation forecasts and the new variables show a high level of skill. Upper-air headline scores also show improvement over the previous AIFS version. The AIFS has been fully operational at ECMWF since the 25th of February 2025.

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Gabriel Moldovan, Ewan Pinnington, Ana Prieto Nemesio, Simon Lang, Zied Ben Bouallègue, Jesper Dramsch, Mihai Alexe, Mario Santa Cruz, Sara Hahner, Harrison Cook, Helen Theissen, Mariana Clare, Cathal O'Brien, Jan Polster, Linus Magnusson, Gert Mertes, Florian Pinault, Baudouin Raoult, Patricia de Rosnay, Richard Forbes, Matthew Chantry. 2025-09-23. An update to ECMWF's machine-learned weather forecast model AIFS. https://arxiv.org/abs/2509.18994

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