The rose diagram shows how commonly and how strongly the wind blows from different directions through a typical southern hemisphere autumn. The longest 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 4858 NWW3 forecasts of wind since since 2007, at 3hr intervals, for the closest NWW3 model node to Sao Pedro, located 19 km away (12 miles). There are insufficient recording stations world wide to use actual wind data. No doubt some coastal places have very localized wind effects that would not be predicted by NWW3.
According to the model, the prevailing wind at Sao Pedro blows from the SSE. If the rose graph shows a fairly circular pattern, it means there is no strong bias in wind direction at Sao Pedro. By contrast, dominant spokes show 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 southern hemisphere autumn, the model suggests that winds are light enough for the sea to be glassy (the lightest shade of blue) about 28% of the time (25 days each southern hemisphere autumn) and blows offshore 44% of the time (40 days in an average southern hemisphere autumn). In a typical southern hemisphere autumn winds exceeding >40kph (25mph) are not expected, but 2 have winds on the range 30-40 (19-25) at Sao Pedro
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.