The rose diagram describes how often and how strongly the wind blows from different directions through a typical March. The largest 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 dark blue. It is based on 1724 NWW3 forecasts of wind since since 2007, at 3hr intervals, for the closest NWW3 model node to Butlers Bay, located 34 km away (21 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 Butlers Bay blows from the SSW. If the rose plot shows a nearly round shape, it means there is no strong bias in wind direction at Butlers Bay. On the other hand, 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. Over an average March, the model suggests that winds are light enough for the sea to be glassy (pale blue) about 33% of the time (10 days each March) and blows offshore 35% of the time (0 days in an average March). During a typical March winds exceeding >40kph (25mph) are not expected, but 0 have winds on the range 30-40 (19-25) at Butlers Bay
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.