Looking one or more months into the future
Our seasonal forecasts provide information about atmospheric and oceanic conditions up to seven months into the future. They are produced every month with a 51-member ensemble at a horizontal resolution of around 36 km.
Annual forecasts are produced with the same system every three months and extend 13 months into the future.
Seasonal charts include differences (or anomalies) from a long-term (model-based) climatology and probabilities of above normal, normal or below normal conditions.
Find out more about how our seasonal forecasts are produced.
Our seasonal forecasting system (SEAS5)
Like the medium- and sub-seasonal-range forecasts, our seasonal forecasts are produced using the ECMWF Integrated Forecasting System (IFS) which uses an Earth system model to represent interactions between the atmosphere, ocean, land and other Earth-system components.
Our seasonal forecasting system uses modelling and initialisation methods which are very similar to ECMWF’s other ensemble forecasts, but the SEAS system is updated less frequently.
El Niño/La Niña forecasts and predictability in the seasonal range
Seasonal predictions rely on aspects of Earth system variability which have long timescales (months to years) and which are, to a certain extent, predictable. The most important of these is the El Niño/La Niña phenomenon.
El Niño refers to periods of anomalous warming in the tropical eastern Pacific (anomalous cooling periods are known as La Niña). El Niño/La Niña events have a strong impact on the weather locally, but also influence global weather patterns. The term Southern Oscillation refers to changes in the tropical atmosphere which tend to accompany El Niño/La Niña events.
Specialised El Niño/La Niña forecast products are provided for our users. See:
Many other potential sources of predictability are also represented in the forecast system.