Probability Forecasts for Water Levels at the Coast of The Netherlands

Sea level probability forecasts are generated by means of the WAQUA/DCSM98 storm surge model with input from ECMWF’s Ensemble Prediction System. For optimum performance with ECMWF input, the model needs to be recalibrated to overcome a systematic underprediction of higher wind speeds. Moreover, an additional calibration of the ensemble with the aid of Rank Histograms is performed. With the calibration, Brier skill scores show that useful probability forecasts can be made for at least 2–5 days ahead. The system runs in experimental real-time mode and results are available on the Internet for forecasters, who used it for the first time during a storm in March 2007.