APPLICATION OF THE DISTANCE OF DISPLACEMENT AND MAXIMUM CORRELATION ON THE PRODUCTS OF ECMWF ENSEMBLE PREDICTION SYSTEM

A new method named the Displacement and Maximum Correlation,which is used to interpret the products of ECMWF Ensemble Prediction System(EPS) automatically, is proposed. The basic assumption is that in a certain degree, the EPS members represent the future weather situations based on the conception of weather regimes defined by the forecasters of the Medium-Range Section in Meteo France. The 500 hPa geopotential height fields from ECMWF EPS are classified. It is shown that the predictability of the atmosphere is relevant to the forecast time and the weather patterns. The new classification method is succinct and intuitive, and the large amount of information contained in the EPS is condensed dramatically. The weather regimes that influence France such as warm blocked flow (BCA), cold blocked flow (BFA), straight flow (RE) and perturbation (PE) are well predicted, but the predictability for the undulating flow (OND) is relatively poor because of its variability.