The following is a description of EFAS v4.8. For an overview of other EFAS releases, please see: EFAS versioning system.


EFAS v4.8 integrates changes in its meteorological forcing with the use of the new version of the ECMWF-ENS ensemble forecasting system, introduced by IFS cycle 48r1. This change in the forcing data has the following impacts on EFAS:

  • Hydrological monitoring:
    • No change in the observation-forced hydrological reanalysis simulations and the ECMWF-HRES-forced forecast initialisation (the so-called fill-up, where observations not yet available).
  • Real time forecasts:
    • The spatial resolution of the forcing increases from 18 km to 9 km for the medium-range EFAS forecasts.
    • The sub-seasonal EFAS forecasts are now produced every day, instead of only twice a week for Mondays and Thursdays. The meteorological forcing comes from the new extended range forecasts in 48r1, produced every day for the 00 UTC cycle, on the same 36 km spatial resolution as before.
  • Reforecasts:
    • EFAS v4.8 will not have a new 48r1-specific hydrological reforecast data set.
  • Seasonal forecasts and seasonal reforecasts:
    • There is no impact on the seasonal hydrological modelling system.

More details on the 48r1 meteorological modelling changes can be found on the Implementation of IFS Cycle 48r1 page.

Technical details

Release date2023-06-27 12UTC
In test suite

2022-06-05 12UTC

EFAS internal release

Archiving of data


Reference climatology (for thresholds/ anomalies)1991-01-01 to 2017-12-31
EFAS Historical1991-01-01 to near present
Horizontal projectionETRS89 Lambert Azimuthal Equal Area Coordinate Reference System (ETRS-LAEA)
Horizontal resolution

5 x 5 km

1 x 1 km for TAMIR products

Temporal resolution

6-hourly for medium range-monthly products, 24-hourly for seasonal

1-hourly for TAMIR products for first 6 hours lead time, 6-hourly thereafter