An overview of techniques for seasonal forecasting

A brief review of the state of seasonal forecasting at the end of the twentieth century is given. The physical basis of seasonal predictability is examined, and the implications of this for forecast strategies considered. The range of methods used for seasonal forecasting is described, with its division into empirical and numerical strategies, and methods for creating multi-model forecasts are discussed. Numerical prediction of climate anomalies is a new and emerging field of human endeavour, and some of its particular challenges are highlighted. Finally, the importance of the development of applications of seasonal forecasts is stressed, and the non-trivial nature of this task is noted.