SEASONAL FORECASTING OF SOUTH-AFRICAN RAINFALL USING A NONLINEAR DISCRIMINANT-ANALYSIS MODEL

Statistical models have been used to provide operational seasonal fore casts of rainfall over southern Africa since 1992. The Climatology Res earch Group has been using a quadratic discriminant analysis model sin ce November 1994. The model relates rainfall over different areas of S outh Africa to principal components of sea-surface temperatures in the Indian, South Atlantic and Pacific Oceans. Details of the model are d escribed in this paper. High forecast-skill levels can be achieved for much of the country throughout the year. The mostly successful perfor mance of the model over a 15-year independent testing period indicates that the model can be used successfully in an operational environment . (C) 1998 Royal Meteorological Society.