Evaluation of ECMWF forecasts, including the 2023 upgrade

Evaluation of ECMWF forecasts, including the 2023 upgrade
Technical memorandum
Date Published
Secondary Title
ECMWF Technical Memoranda
Thomas Haiden
Fernando Prates
Abstract This report provides a summary of ECMWF's forecast performance, covering medium, extended, and seasonal forecast ranges. It includes a short description of the changes implemented as part of the upgrade to model cycle 48r1 in June 2023 and the meteorological impact of the upgrade. Scorecards show that the increase in ENS resolution to match that of the HRES, as well as other changes in cycle 48r1, bring a substantial increase in forecast skill. Headline scores have been adopted by ECMWF in collaboration with its member states to monitor the evolution of various aspects of forecast skill. The report gives updates on these scores, as well as supplementary scores to help provide a more complete assessment of forecast skill. The primary focus of this summary is the medium range, and specifically the forecast performance for upper-air variables. It is shown that in this respect ECMWF has a clear lead among centres. For surface variables, other centres have however partly taken the lead, especially at shorter ranges. Significant improvements of ECMWF due to recent model upgrades can be seen in a substantial reduction of large ENS 10-m wind speed errors. In the extended range, a distinct improvement in the forecasting of 2m temperature anomalies can be seen in week 2 but only marginal improvements in weeks 3 and 4. On the seasonal timescale, the change from La Niña to El Niño conditions was predicted well, and the anomalously warm northern hemispheric summer season 2023 was indicated in the forecasts with a consistent signal.
URL https://www.ecmwf.int/en/elibrary/81389-evaluation-ecmwf-forecasts-including-2023-upgrade
DOI 10.21957/d47ba5263c