Past observations are used to deduce significant correlations between the weather
in the last three months (up to the beginning of the month) and the weather over the next season (from the end of the month). The main predictors are El Niño / La Niña and the trends due to global warming. Overfitting is avoided as much as possible. The forecasts are accessible in interactive web applications.
The system has been documented in Eden et al, 2015.