Long‐range weather forecasting: Value, status, and prospects

Progress in long‐range (1 month to 10 years) weather prediction over the past decade has been reviewed. A considerable body of research on long‐range forecasting has been carried out and published during this period. Many of these studies have produced encouraging results suggesting that some meteorological parameters can be predicted on a seasonal or monthly time scale, at least for certain regions and at certain times of the year. However, operational long‐range forecasts show, at best, only marginal skill and have not improved in recent years. It is suggested that this inability to transfer the level of skill obtained in some research studies into operational practice may be due to a requirement for national weather services to make predictions for all regions under their responsibility and for all times of the year (rather than restricting their forecasts to situations in which there appears to be a reasonable expectation that the forecast will be correct). A second factor that may cause operational forecast skill to be lower than that apparently feasible may be the use of inappropriate statistical techniques in the development of forecast rules.