The meteorological forcing data are all the information necessary to produce hydrological simulations.

• Historical hydro-meteorological time series:  they are used to calibrate the hydrological model, and to define the flood thresholds used to derive some GloFAS products. GloFAS uses the ECMWF-C3S ERA5 reanalysis a proxy meteorological observation and a range of hydrological observational records, managed jointly by the JRC and the Computational centre (COMP)
• Real-time hydro-meteorological observations: they are necessary to define the starting points of the hydrological forecasts, also called initial conditions. GloFAS uses the unconsolidated ECMWF-C3S ERA5-T reanalysis a proxy meteorological observation until it is available, and the first day of the control member of the ECMWF-ENS forecast
• Meteorological forecasts: they are used to provide the future meteorological input to the hydrological models. Ensemble (i.e. multiple realisations -also called ensemble members - from a single numerical weather prediction system) forecasts are used in GloFAS.