The rose diagram shows how frequently and how strongly the wind blows from different directions over a normal September. The largest spokes point in the directions the wind most commonly blows from and the shade of blue implies the strength, with deep blue strongest. It is based on 1680 NWW3 forecasts of wind since since 2006, at 3hr intervals, for the closest NWW3 model node to Nosy Andrea, located 25 km away (16 miles). There are too few recording stations world wide to use actual wind data. Invevitably some coastal places have very localized wind effects that would not be predicted by NWW3.
According to the model, the prevailing wind at Nosy Andrea blows from the SSW. If the rose plot shows a nearly round shape, it means there is no strong bias in wind direction at Nosy Andrea. On the other hand, dominant spokes illustrate favoured directions, and the more deep blue, the stronger the wind. Spokes point in the direction the wind blows from. During a typical September, the model suggests that winds are light enough for the sea to be glassy (pale blue) about 14% of the time (4 days each September) and blows offshore 32% of the time (1 days in an average September). Over an average September winds stronger than >40kph (25mph) are expected on 2 days at Nosy Andrea
IMPORTANT: Beta version feature! Swell heights are open water values from NWW3. There is no attempt to model near-shore effects. Coastal wave heights will generally be less, especially if the break does not have unobstructed exposure to the open ocean.