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In a sub-seasonal or seasonal forecast, especially at the the longer ranges, the day-to-day variability of the river flow, with prediction of the actual expected flood severities, can not be expected due to the very high uncertainties. What is possible, is to rather give an indication of the river discharge anomalies and the confidence in those predicted anomalies. As the forecast range increases, the uncertainty will also generally increase and with it the sharpness of the forecast forecasts will gradually decrease and forecast they will more and more replicate the climatologically expected conditions with some possible positive or negative shift (i.e. anomaly). The generation of the sub-seasonal and seasonal forecast signals and the related products is reflective of this and was designed to deliver a simple to understand categorical information for both the anomalies and the related associated uncertainties present in the forecast, very much relative to the underlying climatological distribution.
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