ECMWF SEAS5 seasonal forecast maps
ECMWF SEAS5 seasonal forecast maps for temperature, precipitation, pressure and SST. Compare SEAS5 with UK Met Office, Météo-France, DWD and CMCC on one shared valid period.
SEAS5 is ECMWF’s fifth seasonal forecasting system, operational since November 2017. It couples the IFS atmosphere with the NEMO ocean and LIM2 sea ice. Monthly forecasts have 51 members initialized on the first of the month; the corresponding hindcasts have 25 members per year.
The imported data use C3S system 51, also labelled SEAS5.1. This identifies revised interpolation to the C3S grid following ECMWF’s computing-system move in 2022. The underlying model integrations are unchanged from SEAS5 system 5. Matching system 51 hindcasts are used here, restricted to the common 1993–2016 reference period.
Configuration source: ECMWF C3S contribution documentation. Identifiers and ensemble schedules: C3S multi-system description.
Coverage and processing on this site
| Centre | European Centre for Medium-Range Weather Forecasts |
|---|---|
| System | SEAS5 (C3S system 51) |
| Forecast members used for probabilities | 51 |
| Hindcast members used for probabilities | 25 per hindcast year |
| Reference period | 1993–2016 hindcast climatology |
| Published grid | C3S 1° global output; ±85° latitude shown. Native model grids differ. |
| Imported lead times | Lead months 1–6; four three-month windows. Some systems forecast further ahead. |
| Variables | 2 m temperature, precipitation, mean sea-level pressure, sea-surface temperature, 500 hPa geopotential height, 10 m wind speed and 850 hPa temperature |
| Products | Ensemble mean anomaly, tercile summary, median exceedance, tercile and outer-quintile probabilities |
| Source datasets | C3S monthly anomalies and monthly member statistics. Z500 and T850 use the corresponding pressure-level anomalies and pressure-level member statistics. |
These details describe the imported August and September 2026 runs. Each import resolves the system identifier for that initialization and checks it against the source metadata. Imports are run manually; a new monthly forecast may be available from the centre before it appears here. Check the initialization and system on the map panel.
Monthly ensemble-mean anomalies are supplied by C3S. Probabilities and three-month products are derived locally from operational C3S data; they are not synthetic sample forecasts. Member counts above describe the local probability calculation, not necessarily the full ensemble offered by a centre. See the C3S product definitions and the probability guide for reference and processing conventions.
ECMWF against the other models
Each link opens ECMWF next to one other centre for the same October 2026 initialization, with a shared valid period and scale. Differences can reflect model formulation, initialization, ensemble sampling and each system’s hindcast climate; they do not establish which model is more skilful.
- ECMWF vs UK Met Office GloSea6-GC5.1: January 2027 temperature
- ECMWF vs Météo-France System 9: January 2027 temperature
- ECMWF vs DWD GCFS 2.2: January 2027 temperature
- ECMWF vs CMCC SPS4: January 2027 temperature
- ECMWF vs UK Met Office seasonal forecasts
- Europe seasonal temperature outlook: five models compared
- How the seasonal outlook changed between monthly runs