ECMWF has pioneered a system to predict forecast confidence. This system, operational at ECMWF since 1992, is the Ensemble Prediction System (EPS). A new leaflet on EPS has been published on the ECMWF web.
Scientists at ECMWF have been constantly working to further improve the performance and utility of the EPS forecasts and products. Over the years, substantial improvements have been made in three key areas: in the model formulations and the data assimilation procedure used to estimate the initial conditions, in the use of more and better weather observations, and in the simulation of the effect of uncertainty in initial conditions and model equations. As a result, the ECMWF EPS is the most skilful ensemble prediction system compared to any other existing system in the world.
The 51 EPS forecasts can be used to predict the probability that a particular weather event of interest might occur. For instance, a government agency might be interested in knowing whether severe flooding might occur in a certain part of the country. The EPS provides an estimate of the likelihood of such an event. Also, EPS-based probabilistic forecasts of tropical cyclone tracks can give decision makers extremely valuable information on the probability of occurrence of these extreme weather conditions.
A new leaflet on the ECMWF ensemble prediction system has been published on the ECMWF website.