Potential Benefits of Using Probabilistic Forecasts for Waves and Marine Winds Based on the ECMWF Ensemble Prediction System

Abstract

Abstract The potential benefits of using the ECMWF Ensemble Prediction System (EPS) for waves and marine surface winds are demonstrated using buoy and platform data as well as altimeter data. For forecasting purposes, the spread of the different forecasts in the ensemble may indeed be regarded as a measure of the uncertainties in the deterministic predictions. In order to demonstrate this point, a new method is presented in which the ensemble spread is divided into different classes. An upper bound for the model errors is established by calculating the corresponding percentiles of the errors for each separate class. Using this upper bound for the model errors, a strong correlation between the ensemble spread and the deterministic forecast skill is shown. The reliability of the probability forecasts as derived from the EPS for wind and waves is found to be good. However, the reliability diagrams indicate a small tendency for overconfidence in the wave probability forecasts for waves above 6 and 8 m. This i...