What is GloFAS 30-day?
How are GloFAS 30-day forecasts generated?
GloFAS 30-day modelling chain is based on a coupled land-surface and hydrological model forced by an ensemble of meteorological forcings. A 5-day monitoring analysis of the latest observations, either based on the latest ECMWF reanalysis when available, or day-1 of ECMWF ENS control forecast, is use to initialise the forecasts, followed by medium and extended range ensemble forecasts up to 30 days from the ECMWF Integrated Forecast System ENS. The resulting 30-day simulated daily hydrological forecasts are compared with reference discharge runs obtained from the same modelling chain. This results in a set of probabilities of exceeding pre-defined flood thresholds of different severity.
Schematic of GloFAS 30-day
Which products does GloFAS 30-day offer?
- Threshold exceedance icons: A summary map at regional scale, where GloFAS 30-day forecasts are shown as warning icons for over 2000 reporting points. The icons display the overall evolution of the discharge with the severity thresholds provided for the next 30 days.
- River network probabilities: A summary map at river scale, where GloFAS 30-day forecasts are shown for the GloFAS river network of all catchments larger than 1000 km2. The map shows the probability of the streamflow forecast to exceed two pre-defined thresholds (5-year and 20-year levels) within the next 30 days.
- Forecast details: Additional information for selected river points, including time evolution of the streamflow forecast for the next 30 days, and a summary of forecast probabilities of five previous GloFAS 30-day forecasts showing consistency in the forecast signal.
- Precipitation maps: A summary map at regional scale, showing ensemble median and probability of first 10-day precipitation forecast totals to exceed three pre-defined threholds.
GloFAS 30-day reference discharge runs
GloFAS 30-days reference discharge runs are a collection of discharge simulations as close as possible to GloFAS 30-day operational system.
GloFAS 30-day forecast reruns are forecast simulations performed for a set of past dates, based on a configuration as close as possible to GloFAS 30-day operational setting, initialised using GloFAS 30-day hydrological reanalysis. GloFAS 30-day forecast reruns can be used to analyse GloFAS forecast skill systematically over a long period.
GloFAS 30-day discharge thresholds are a set of maps of discharge magnitudes corresponding to the 2-, 5- and 20-year return period floods (respectively called Medium, High and Severe Awareness Levels). They are generated by fitting a Gumbel extreme value distribution to the annual maxima series extracted from GloFAS 30-day discharge timeseries of the hydrological reanalysis using the method of L-moments. GloFAS 30-day discharge thresholds are used to generate flood awareness forecast maps.
GloFAS 30-day data
- 51-member ensemble real-time daily discharge forecasts for 30 days (GloFAS 30-day).
- A proxy-observation deterministic daily discharge simulation, based on the latest ECMWF reanalysis (GloFAS 30-day discharge time series from GloFAS 30-day hydrological reanalysis).
- Ensemble daily discharge forecast reruns; the frequency (daily/twice weekly Monday and Thursday) and ensemble size depends on the forecast reruns period (GloFAS 30-day forecast reruns).
- A set of deterministic flood thresholds corresponding to the 2-, 5- and 20-year return period discharge levels (GloFAS 30-day discharge thresholds).