Grib files weather data are derived from mathematical models. They’re not always accurate!
In addition, it is necessary to match the chosen model with your type of navigation.
The GFS model covers the entire earth with a grid of 0.25° (about 15 NM). It will not be able to take into account local phenomena. And even offshore, the GFS could be wrong! They’re just forecasts.
One of SailGrib’s strengths is that you have access to several models!
For a coastal navigation, you can for example choose the high resolution models;
- in the US, the NAM models from the NOAA.
- in Europe the Arpège Europe model from Météo France.
- in France, you can get the Arôme model from Météo France, a very high resolution model.