Page History

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• CEMS-Flood sub-seasonal products are produced every day, showing calendar week river discharge anomalies up to 6 weeks divided into 7 categories, from extreme low to extreme high compared with a forecast-range dependant climatology
• CEMS-Flood seasonal products are produced every month, showing monthly river discharge anomalies up to 7 months divided into 7 categories, from extreme low to extreme high compared with a forecast-range dependant climatology
• Both sub-seasonal and seasonal products are available for the EFAS and GloFAS systems, and shown as maps over the full domain (river network and basin summary) with additional information available for reporting points. Each product is plotted for each lead time, with the possibility to navigate between maps.Rationale
• Antecedent condition and
overview
• climatology

Background

In a sub-seasonal or seasonal forecast, especially at the the longer ranges, the day-to-day variability of the river flow can not be predicted due to the very high uncertainties in numerical weather prediction. 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 also generally increases and with it the sharpness of the forecasts will gradually decrease; subsequently, the forecasts will more and more replicate the climatologically expected conditions with some possible positive or negative shift (i.e. anomaly). 

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The CEMS-Flood sub-seasonal products cover calendar week periods (i.e. always Monday-Sunday), while the CEMS-Flood seasonal products are valid for whole calendar month periods. The forecast signal is derived from the relationship between the calendar weekly or monthly averaged river discharge and the climatological distribution of the historical weekly- or monthly-averaged values. While consistency checks naturally works for the calendar months, the fixed calendar weekly lead times in the sub-seasonal allow the users to directly compare forecasts from different forecast runs, as the verification period is fixed onto the calendar weeks. This way, the evolution of the subsequent daily sub-seasonal forecast runs (always at 00 UTC) can be monitored by looking at the exact same verification period.

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