GribStream Blog
ECMWF takes AIFS-ENS operational (ensemble AI forecasts)
ECMWF moved AIFS-ENS into operations on July 1, 2025, running a 51-member AI ensemble alongside the physics-based IFS ensemble.
On July 1, 2025, ECMWF moved the ensemble version of its Artificial Intelligence Forecasting System into operations. The new system is called AIFS-ENS, and it runs side by side with the traditional physics-based IFS ensemble.
What is AIFS-ENS
AIFS-ENS is ECMWF's AI-based probabilistic global forecast. It uses a stochastic ML model trained on reanalysis and fine-tuned on operational analyses, then initializes member-for-member from the IFS ensemble. The operational configuration provides:
- 51 members (50 perturbed + 1 control).
- 00/06/12/18 UTC cycles.
- 6-hourly steps out to 360 h (15 days).
- 0.25 deg global grid (open-data subset).
Why it matters
Operational AI ensembles make it possible to compare AI vs. physics guidance using the same horizons and a consistent ensemble structure. That is valuable for:
- Uncertainty-aware planning using probabilistic thresholds.
- Benchmarking AI guidance against the IFS ensemble.
- Scenario analysis for energy, aviation, marine, and hydrology.
What this means for GribStream users
GribStream supports both the deterministic AIFS Oper and the ensemble AIFS-ENS. That makes it easy to:
- Compare AIFS-ENS vs. IFS ENS for the same events.
- Run backtests on AI guidance using as-of time travel.
- Build ensemble percentiles and event probabilities.