One session. More than one perspective.
Comparing models helps you distinguish a consistent outlook from a surf plan that needs room to change.
Why forecasts differ
Models use different methods to process observations and calculate how weather will evolve. Differences in storm development, wind strength and timing can produce different swell outlooks for the same place.
Windswelltide lets you compare the Euro (ECMWF) and US (GFS), alongside other available models. Compare the same location, forecast hours, units and variables. Check the run details too: a difference may reflect a newer update as well as a different model.
What does agreement look like?
Same spot, same morning. Switch the example to see how the decision changes.
| Condition | Euro · ECMWF | US · GFS |
|---|---|---|
| Swell | 2.0 m · 15 s | 1.9 m · 15 s |
| Direction | SW | SW |
| Wind | Offshore · 5 kt | Offshore · 6 kt |
Both models suggest similar swell and light offshore wind. That is a more consistent signal for this window, not a guarantee.
Offshore assumes a suitable coastline orientation. Values are invented to explain comparison.
Read agreement—and disagreement
When models agree: look for consistency in arrival time, swell period and direction as well as height. Similar local wind forecasts make a session easier to plan, but models can share errors. Two matching forecasts are not a measured probability of good surf.
When models differ: identify the difference that changes your decision. A few hours in swell timing or an earlier onshore wind can matter more than a small difference in height. Keep a backup spot or a flexible departure time and check the next update.
Compare the whole surf window
- Height + period: together they describe more of the swell than height alone. Longer-period swell at the same offshore height generally carries more deep-water wave power.
- Direction: check which coastline is exposed and which breaks are sheltered by headlands or islands.
- Wind + tide: look for the hours when swell, local wind and your preferred tidal stage overlap.
No model is always best at every break. Build experience of how each behaves locally, and avoid choosing a forecast simply because it promises better waves.