ECMWF Model Upgrade Improves Extended-Range Weather Forecasts

The upgrade:

• improves forecast quality in the tropics, enabling better predictions in the extended range in Europe and elsewhere, notably at weeks three and four
• improves 2-metre temperature forecasts, including in Europe
• brings better predictions of rain in coastal areas as a result of improved cloud physics
• improves high-resolution forecasts in situations marked by rapid interactions between sea ice, the ocean and the atmosphere, such as the passage of tropical cyclones or rapid changes in sea ice cover

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Up to now, dynamic ocean, sea ice and atmosphere coupling has only been applied in medium-range ensemble forecasts (18 km horizontal resolution), extended-range forecasts and seasonal forecasts. The upgrade extends this coupling to ECMWF's medium-range high-resolution forecasts (9 km horizontal resolution). In addition, the upgrade enhances coupling in the tropics for both high-resolution and ensemble forecasts. As a result, the IFS is now more consistent and seamless across different timescales and spatial resolutions.

Other changes include:

• a better use of observations, notably through a scheme to account for the horizontal drift of radiosondes during their ascent
• the use of more satellite observations, including non-surface-sensitive infrared channels over land
• more realistic ocean depth (bathymetry), which mostly affects the wave fields in coastal areas
• the introduction of new products useful in the prediction of severe weather, including forecasts of lightning flash density, and of maximum convective available potential energy (CAPE) over the last six hours of the forecast.

The changes are based on research by scientists at the Centre, often in collaboration with other scientists in ECMWF's Member States and beyond. Accounting for the drift of radiosondes has notably been made possible by a new data format providing full position information that is being rolled out across the world.

Director of Forecasts Florian Pappenberger said: "The new model version brings pronounced improvements in upper-air predictions in the tropics, especially for wind and temperature. It is exciting to see the consistent gains in extended-range forecasts and the overall improvement in 2-metre temperature both in high-resolution and ensemble forecasts, particularly for Europe. In addition, near-coastal precipitation in warm-rain dominated situations is significantly improved, addressing a long-standing issue with our model."

Director of Research Andy Brown said: "This is a substantial upgrade which marks a milestone towards our Strategy to 2025. The Strategy calls for a more seamless forecasting system by making our different forecasts more coherent. The enhanced coupling across all time ranges brings us one step closer to seamlessness. In addition to the important immediate benefits the upgrade delivers, it prepares the ground for further sustained progress."

Notes for editors 

The European Centre for Medium-Range Weather Forecasts (ECMWF) is an independent intergovernmental organisation supported by 34 states, established in 1975. ECMWF's core mission is to produce numerical weather forecasts, carry out scientific and technical research to improve forecast skill, and to maintain an archive of meteorological data.

For more details, please see: https://www.ecmwf.int/en/about/media-centre/news/2018/ifs-upgrade-improves-extended-range-weather-forecasts   

For more information, please contact: ECMWF Press Office, +44-118-949-9000, pressoffice@ecmwf.int