GFS vs ECMWF IFS
GFS or ECMWF: which global model should I use?
They are the two global models most sailors use. ECMWF is generally regarded as the more skilful of the two, especially beyond three days. GFS is free of restrictions, goes out to 16 days and is the model nearly every GRIB service and app builds on.
| GFS | ECMWF IFS | |
|---|---|---|
| Provider | NOAA / NCEP | ECMWF |
| Type | Global model | Global model |
| Area | Global | Global |
| Grid size | about 13 km | about 9 km |
| Updates | 4 times a day | 4 times a day |
| Looks ahead | 16 days | 15 days |
| Data licence | Public domain (US Government) | CC-BY-4.0 (open data) |
Choose GFS when
- You want the longest outlook (16 days) or the most widely supported GRIB source.
- You are in or near US waters, where GFS and its companion models are home-grown.
- You want to compare against what most other sailors are looking at.
Choose ECMWF IFS when
- You are planning a passage more than three days ahead and want the model usually trusted most there.
- You are tracking storms or tropical systems in the medium range.
- You want a second opinion to set against GFS.
On the water
Use both. When they agree, confidence is higher. When they disagree about a front or low-pressure system, take that as a sign of uncertainty and look at an ensemble.
More: Which model for my area?
Figures come from the Ilma catalog and the providers' own pages. Forecast skill changes as models are upgraded, so this page describes what each model is built for, not a ranking.