Evolution of Ensemble-based PDF of Initial States

Over the past few years ensemble prediction has come to the fore as a major element in defining the future of numerical weather predicion (NWP) and operational weather forecasting. This stems basically from convergence of increasing recognition of the importance of explicitly addressing the intrinsic uncertainties in forecasts with existing/prospective super-computer resources and development of ensemble strategies.

One of the ultimate usages of ensemble forecasting is probabilistic forecasts. A critical issue in ensemble- based probabilistic approach is that given a probability distribution of initial atmospheric states, is it possible for an IMPERFECT model to accurately predict the TRUE evolution of that initial pdf? Under an ideal environment, this issue was studied with an ensemble prediction system (EPS) based on a simple model. If time permits, a similar study will be conducted with a state-of-the-art NWP model and then reported in this meeting.