The rose diagram describes how frequently and how strongly the wind blows from different directions over a normal October. The largest spokes point in the directions the wind most commonly blows from and the shade of blue indicates the strength, with the strongest winds shown by the darkest shade of blue. It is based on 1736 NWW3 forecasts of wind since since 2006, at 3hr intervals, for the closest NWW3 model node to Topsail Island, located 45 km away (28 miles). There are not enough 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 Topsail Island blows from the SE. If the rose diagram shows a close to circular outline, it means there is no strong bias in wind direction at Topsail Island. By contrast, dominant spokes represent favoured directions, and the more the darkest shade of blue, the stronger the wind. Spokes point in the direction the wind blows from. During a typical October, the model suggests that winds are light enough for the sea to be glassy (pale blue) about 9% of the time (3 days each October) and blows offshore 33% of the time (8 days in an average October). Over an average October wind stronger than >40kph (25mph) was forecast for only a single days at Topsail Island
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.