Report on calibrating the site-specific probability forecasts from the ECMWF Ensemble Prediction System
DENHOLM-PRICE [J.C.W.] ; MYLNE, K.R.
The Previn Development Project was intended to improve the use of the Ensemble Prediction System (EPS) from the European Centre for Medium-Range Weather Forecasting (ECMWF) as currently implemented in Previn (which stands for 'PREdictability VisualisatioN')?. Here we describe the part of the project designed to improve the reliability of the site-specific probability forecasts derived from the EPS data (The original Previn system was uncalibrated.) Calibration is performed in two stages. Firstly rank histograms from past verification are used to re-weight ensemble members, giving improved probabilities for even threshold within the spread of ensemble members. Secondly to calibrate thresholds lying outside the spread of the ensemble. Weibull distributions are fitted to past ensemble outliers. This report describes the calibration processes, the significance of testing of fitted distributions and demonstrates the significant improvements in probability forecasts achieved.
Accès à la notice sur le site du portail documentaire de Météo-France