...
- CEMS-Flood sub-seasonal products are produced every day, showing calendar week river discharge anomalies up to 7 6 weeks divided into 5 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 5 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 the between maps.
- Rationale and overview
...
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 to be simulated 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).
The generation of CEMS-Flood Flood sub-seasonal and seasonal forecast signals and 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.
...
The generation of the sub-seasonal and seasonal forecast signal relies on few major steps, illustrated by a flowchart in Figure 1. The forecast anomaly and uncertainty signals is are derived by comparing the real time forecast (top left section in Figure 1) to the 99-value percentile climatology. The climatology is generated using reforecasts over a 20-year period, which provides range-dependent climate percentiles that change with the lead time. The climate generation is described in the bottom right corner of Figure 1.
...