Models from different organisations
ECMWF develops the Integrated Forecasting System. GFS is the global system operated by NOAA/NCEP in the United States. ICON is developed by the German Weather Service, DWD, with global and higher-resolution regional configurations.
Each system uses a different dynamical core, parameterisations, observation inputs and assimilation process. No model is best for every region, variable and forecast day.
Resolution and forecast range
A finer grid can describe mountains and coastlines better but does not guarantee the exact position of a thunderstorm. Actual skill also depends on the initial state, model physics and type of weather event.
Run cycles and available forecast ranges differ. A comparison should show issue time and avoid placing an old run of one model beside a newer run of another as though they were simultaneous.
Why ensembles and agreement matter
One deterministic run is only one possible scenario. Ensembles perturb the initial state or physics and reveal how stable the outcome is. Confidence generally increases when many members and different systems agree.
The e-meteo combined forecast summarises available solutions and their spread. It does not replace original providers or remove uncertainty, especially beyond the first week.
This guide is educational. For safety-critical decisions, use current observations and follow the competent official authorities.