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Observational probability method to assess ensemble precipitation forecasts

It is common practice when assessing the skill of either deterministic or ensemble forecasts to consider the observations with no uncertainty. Observation uncertainty may be associated with different causes and the present paper discusses the uncertainty that derives from the mismatch between model‐generated grid point precipitation and locally measured precipitation values. There have been many attempts to add uncertainty to the verification process; in the present paper the uncertainty is derived from the observed precipitation distribution within grid boxes of assigned resolution. The Brier skill score (BSS) and the area under relative operating characteristic curve skill score calculated utilizing the verification method which includes observational uncertainty (O‐OP), are compared to analogous scores obtained from standard verification methods. The scores are calculated for two different forecasting systems: the European Centre for Medium‐Range Weather Forecasts Ensemble Prediction System and the Spanish Meteorological Agency Short‐Range Ensemble Prediction System.