Boating in the Western Mediterranean: the best day to go

The crossings here are long enough that the sea changes while you are on them. The mistral funnels down the Rhône valley and out over the Gulf of Lion, the tramontana does much the same thing further west, and either can leave a short, steep sea running for a day after the wind itself has gone. The Bouches de Bonifacio add their own squeeze to whatever is already blowing.

Bonasea simulates the crossing in time instead of scoring one point in it: at your cruising speed the boat is asked for the forecast at the position it will be in, at the hour it will be there. Short-period wind sea is penalised for steepness, a long swell underneath is discounted, and the worst stretch of the route pulls the day down rather than being averaged away. The AROME model covers the French coast and the western basin, which is where the mistral gradients live.

Depth figures are modelled averages rather than a survey of your bay, and the comfort score is an estimate from weather models rather than a promise. Bonasea does not replace official charts, publications, regulations or the skipper’s judgement. Read the warnings for these waters before you leave, and trust your echo sounder over the app.