You can access seasonal forecast models hindcast and forecast data on the C3S Climate Data Store https://cds.climate.copernicus.eu
Forecast
Forecast products : Spatial maps, Oceanic plums , Climagrams
Climatology
model climatology (period 1993-2016)
Scores
Probabilistic and deterministic scores, calculated over the hindcast period (1993-2016)
Data
Data from Seasonal Forecast models