The Integrated Forecast System (IFS) is an operational global meteorological forecasting model. IFS is developed and maintained by the European Centre for Medium-Range Weather Forecasts (ECMWF) based in Reading, England. Because of its source, it is often known as the "ECMWF" or the "European model" in North America, to distinguish it from the American Global Forecast System (GFS). It is one of the predominant synoptic-scale medium-range models in general use worldwide; its most prominent rivals in the 6–10 day medium range include the GFS and the Canadian Global Environmental Multiscale Model (GEM).
The IFS is a global model that runs every twelve hours. Its output runs out to fifteen days in one-day intervals (although output is only made available to most members of the public out to 7 to 10 days, depending on the variable). The operational model runs both in a deterministic forecast mode and as a 51-member ensemble. The current deterministic mode has a horizontal resolution of 16 km while the ensemble prediction systems have resolutions of 32 and 64 km, and 137 layers in the vertical resolution in the deterministic compared to 91 layers in the ensemble; both modes' vertical layers follow terrain at low levels. The IFS, like the GFS, uses spectral representation rather than a grid-based system. Because the IFS only offers output on a day-by-day interval, each individual ECMWF member country typically runs its own synoptic-scale forecast for the shorter ranges of 5 days or less, separate from the IFS, with smaller time intervals (examples include the French ARPEGE, British Unified Model and German GME).
Information from the IFS is proprietary and copyrighted, though the ECMWF has made a limited amount of the model's most important calculations available to the public "with no restrictions."