This picture describes how often and how strongly the wind blows from different directions through a typical August. 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 Pors Carn, located 22 km away (14 miles). There are too few 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 Pors Carn 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 Pors Carn. On the other hand, dominant spokes illustrate favoured directions, and the more dark blue, the stronger the wind. Spokes point in the direction the wind blows from. Over an average August, the model suggests that winds are light enough for the sea to be glassy (the lightest shade of blue) about 9% of the time (3 days each August) and blows offshore 54% of the time (11 days in an average August). In a typical August wind stronger than >40kph (25mph) was forecast for only a single days at Pors Carn
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.