This chart shows how commonly and how strongly the wind blows from different directions through a typical year. The longest spokes point in the directions the wind most commonly blows from and the shade of blue implies the strength, with the strongest winds shown by dark blue. It is based on 20052 NWW3 forecasts of wind since since 2006, at 3hr intervals, for the closest NWW3 model node to Charleston, located 38 km away (24 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 dominant wind at Charleston blows from the WSW. If the rose graph shows a fairly circular pattern, it means there is no strong bias in wind direction at Charleston. Converseley, dominant spokes show favoured directions, and the more deep blue, the stronger the wind. Spokes point in the direction the wind blows from. Over an average year, the model suggests that winds are light enough for the sea to be glassy (light blue) about 21% of the time (77 days each year) and blows offshore 34% of the time (95 days in an average year). In a typical year winds stronger than >40kph (25mph) are expected on 22 days at Charleston
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.