The rose diagram describes how often and how strongly the wind blows from different directions through a typical March. The longest 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 dark blue. It is based on 1724 NWW3 forecasts of wind since since 2007, at 3hr intervals, for the closest NWW3 model node to Derrynane, located 31 km away (19 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 Derrynane blows from the WSW. If the rose plot shows a nearly round shape, it means there is no strong bias in wind direction at Derrynane. Converseley, dominant spokes show favoured directions, and the more dark 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 (light blue) about 2% of the time (1 days each March) and blows offshore just 13% of the time (2 days in an average March). In a typical March winds stronger than >40kph (25mph) are expected on 3 days at Derrynane
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.