A pan-European service for hydrological seasonal forecasts at C3S

As contractor and sub-contractor for C3S, SMHI and WU-DES have set up a multi-model operational service for hydrological seasonal forecasts. The service currently produces forecasts of monthly mean river discharge for a pan-European domain using several hydrological models, namely E-HYPEcatch, on irregular catchment delineations, and E-HYPEgrid and VIC-WUR on regular 5km gridded drainage network of EFAS. Also, the EFAS-Lisflood forecasts from the separate ECMWF production line are included in the final data set. All forecasts use the SEAS5 meteorological forecasts with 51 ensemble members. The data from all models are available from the CDS data portal for a re-forecast (https://doi.org/10.24381/cds.13c18212) and a forecast period (https://doi.org/10.24381/cds.52f45864). Further, the most probable forecast is displayed in an online application (https://cds.climate.copernicus.eu/cdsapp#!/software/app-hydrology-seasonal-forecast-explorer?tab=app).

Ongoing work is aimed at introducing a second meteorological forecasting system, and adding more output variables at a higher daily temporal resolution. The quality of the forecasts is at this point mainly addressed by working on the input data and statistical downscaling and bias adjustment. The new system is expected to be operational in mid-2024.