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The main prediction system currently used for seasonal timescales is GloSea4. It is an ensemble prediction system using a coupled ocean-atmosphere model (variant of HadGEM3), to generate probabilistic forecasts up to six months ahead. GloSea4 includes uncertainties due to initial conditions and model formulation.

In a major change from the previous seasonal forecasting system, GloSea4 is fully integrated in the model-development cycle. This is expected to lead to faster improvements in forecasting skill for regional, seasonal scales.

The output from the system is used to generate products.

Key aims

• To develop an operational forecasting system.

• To contribute to model development.

• To generate products required by World Meteorological Organization, from its global producing centres of long-range forecasts (of which the Met Office is one).

Current research

• Model initialisation, including ocean data assimilation

• Representation of model uncertainties

• Calibration of model output and verification