Page History

The following is a description of GloFAS v4.

3, available as fully operational GloFAS from

04 June 2025.

For an overview of other GloFAS releases, please see : GloFAS versioning system.

Summary

GloFAS GloFAS v4.2 3 introduces several minor changes to the system, including:

• A new design of long-range forecasts with newly added sub-seasonal and upgraded seasonal products, including:
  • Similar methodologies for both seasonal (monthly anomalies) and sub-seasonal (weekly anomalies) products, with basin averages and river network information available. 
  • Generation of expected forecast anomaly and associated uncertainty signal based on the anomaly of individual ensemble members against reforecast-based climatological distributions
  • New mapviewer functionality with selectable forecast horizon for the river network and basin summary outlook maps
  • Pop-up windows showing the evolution of antecedent conditions and forecast anomalies against background climatology with details on forecast probabilities and expected anomalies for selected reporting points
  • Please note, CEMS-Flood seasonal forecasts are available after SEAS5 is published, around the 8th of each month.
  • For details on the products and methodology see: GloFAS sub-seasonal and seasonal forecast products, GloFAS seasonal outlook, GloFAS sub-seasonal outlook, GloFAS Hydrological Products Overview, GloFAS sub-seasonal and seasonal forecasting & CEMS-Flood sub-seasonal and seasonal forecasting
• The forecast horizon for GloFAS medium-range products have been reduced to 15 days on GloFAS-IS. The 15-day forecast horizon affects the products in the Reporting Points pop-up window (hydrographs, consistency plots, etc) and the Flood Summary layers. outlooks beyond 15 days are now provided as weekly river discharge anomalies in the sub-seasonal forecast products, consistently with the decreasing predictability of flood events for increasing lead times and increasing predictability of weekly products. For details on changes to how the GloFAS medium-range (15-day) products are displayed, see: GloFAS medium-range forecasting, GloFAS Hydrological Products Overview, GloFAS Reporting Points , Overall GloFAS products summary, GloFAS medium-range forecast products, and GloFAS Flood Summary.
• GloFAS Forecast Skill Product:  the forecast skill layer displays the skill of the medium-range forecasts and to 15 days. For more details on the forecast skill layer, see: GloFAS forecast skill and GloFAS forecast skill product
• Removal of reporting points with upstream area <250km² on GloFAS-IS. The minimum upstream area of fixed reporting points has been limited to 250 km2 for higher consistency with model spatial resolution (0.05 degrees).
• Update of reporting points: one new point in Nepal and three reporting points remapped to GloFAS river network (one in China, Finland, and Uganda).
• New Country Boundaries layer on GloFAS-IS for easy identification of country borders on the map viewer. For details on the new layer see: GloFAS Static Layers Overview
• The status of the EWDS availability is now showing on web interface (as small, green/orange/red dot beside 'Live' in the top menu and then on the Live page itself). If the dot is orange users may experience longer waiting times when downloading requested data
• The GloFAS medium-range forecast skill layer has been updated in two key ways:
  • Expanded Reforecast Coverage: In GloFAS v4.0, the forecast skill layer was initially calculated using only the reforecasts for April, May, and June, which were the months available at the time of release. The forecast skill layer in GloFAS v4.2 has now been recalculated using a complete set of reforecasts, covering the entire year. For details see: GloFAS v4 forecast skill.
  • Updated Climatological Benchmark Period: The reference period for the climatological benchmark used to calculate forecast skill has been changed from a 40-year period (1979-2018) to a more recent 20-year period (2003-2022). This update serves several purposes: (1) it provides a more relevant benchmark by using recent data, (2) it aligns the benchmark period with the reforecast period, and (3) it avoids potentially inflating the perceived skill of the forecasts, as a 40-year climatology benchmark may be too easily outperformed. For details see: GloFAS forecast skill
• The GloFAS data dissemination description was updated, including a new catalogue of available data and products for time critical FTP download (FTP).
• Medium-range reforecasts
• Change in the reforecast dates now released every month on the 1/5/9/13/17/21/25/29 (excluding 29 February) and not every Monday and Thursday as previously done. This may have an implication for users using CEMS-Flood reforecast data in their downstream application as the scheduling of reforecast date will change. See Implementation of IFS Cycle 49r1 for more details.
Temporary freeze of medium-range reforecasts available from the EWDS, with no update of the dataset from GloFAS v4.2 release date. If you require access to the reforecast data, please get in touch with us via the ECMWF Support Portal using the title 'Access to GloFAS Reforecast Data' when creating the ticket. Information on how to raise a ticket in our support portal is available here.

This upgrade of GloFAS has no impacts on the GloFAS modelling results.

Technical details details