The figure shows how frequently and how strongly the wind blows from different directions over a normal September. The biggest spokes point in the directions the wind most commonly blows from and the shade of blue suggests 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 D and W, located 49 km away (30 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 dominant wind at D and W 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 D and W. Converseley, 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 (light blue) about 5% of the time (2 days each September) and blows offshore 6% of the time (0 days in an average September). Over an average September winds exceeding >40kph (25mph) are not expected, but 0 have winds on the range 30-40 (19-25) at D and W
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.