This picture shows how frequently and how strongly the wind blows from different directions through a typical northern hemisphere autumn. The longest spokes point in the directions the wind most commonly blows from and the shade of blue suggests the strength, with the strongest winds shown by the darkest shade of blue. It is based on 5144 NWW3 forecasts of wind since since 2006, at 3hr intervals, for the closest NWW3 model node to Ile de Noirmoutier, located 16 km away (10 miles). There are insufficient recording stations world wide to use actual wind data. Without question some coastal places have very localized wind effects that would not be predicted by NWW3.
According to the model, the prevailing wind at Ile de Noirmoutier blows from the W. If the rose diagram shows a close to circular outline, it means there is no strong bias in wind direction at Ile de Noirmoutier. Converseley, dominant spokes illustrate favoured directions, and the more deep blue, the stronger the wind. Spokes point in the direction the wind blows from. Over an average northern hemisphere autumn, the model suggests that winds are light enough for the sea to be glassy (the lightest shade of blue) about 9% of the time (8 days each northern hemisphere autumn) and blows offshore 33% of the time (28 days in an average northern hemisphere autumn). In a typical northern hemisphere autumn winds stronger than >40kph (25mph) are expected on 7 days at Ile de Noirmoutier
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.