This paper has been written to mark 25 years of operational medium-range
ensemble forecasting. The origins of the ECMWF Ensemble Prediction System are
outlined, including the development of the precursor real-time Met Office
monthly ensemble forecast system. In particular, the reasons for the
development of singular vectors and stochastic physics - particular features of
the ECMWF Ensemble Prediction System - are discussed. The author speculates
about the development and use of ensemble prediction in the next 25 years.Comment: Submitted to Special Issue of the Quarterly Journal of the Royal
Meteorological Society: 25 years of ensemble predictio