The wind is unreliable and not good to sail

Why are you so unprecise

Bzh 29
Ventusky offers 10 or more weather models — it always depends on which data source you select. We are a visualization platform. Unfortunately, you did not specify either the location or the model you used.

It might also be useful to turn off interpolation in the Settings. This allows you to see exactly which area the model covers and what its actual resolution is. These are precisely the kinds of features Ventusky offers and excels at.