Probabilistic Evaluation of the Multicategory Seasonal Precipitation Re-Forecast

The Meteo-France seasonal forecasting system 7 provides a 7-month forecast range with 25 ensembles. precipitation re-forecast (from May to November 1993–2015) was evaluated by the Brier score in terms of accuracy and reliability based on tercile probabilities. Multiple analyses were performed assess robustness score. These results show that spatial distribution depends significantly thresholds, reference data, sampling methods, ensemble types. Large probabilistic errors over dry regions land Nino Pacific can be reduced adjusting thresholds. identified when they insensitive different analysis methods. All detected increase/decrease lead time tropical Indian/Pacific Ocean. intra-seasonal reveals some these are inherited from monthly forecasts, which may related large-scale, short-term variability modes. A new confidence interval calculation formulated for “uncertain” case data. at 95% level mean entire region quantified. best estimations ~6% both above below-normal terciles.