If you want to force SailGrib to avoid areas with heavy or light winds, you can specify here upwind (TWA <=90°) and downwind (TWA>90°) wind limits. Note that by setting these limits, you create discontinuities in the routing and you might end up with no route…
For example, let us say you want to sail on a first 31.7 from Sardigna to Marseille and leave Sardigna on March 13th at 09:00 UTC. If you do not set any wind limit, the duration of the trip should be around 1 day 14hours and the max wind speed on the best route will be 33 knots. If you set a max upwind  wind speed of 30 knots, the best route is more to the east, the duration is around 1 day 15 hours and the max wind speed 23 knots. It appears to be a better option (but may be, you should just wait for a day…).
