This picture shows how commonly and how strongly the wind blows from different directions through a typical northern hemisphere spring. The largest spokes point in the directions the wind most commonly blows from and the shade of blue implies the strength, with the darkest shade of blue strongest. It is based on 4858 NWW3 forecasts of wind since since 2007, at 3hr intervals, for the closest NWW3 model node to Treasure Island, located 22 km away (14 miles). There are too few recording stations world wide to use actual wind data. Invevitably some coastal places have very localized wind effects that would not be predicted by NWW3.
According to the model, the most common wind at Treasure Island blows from the SSW. If the rose graph shows a fairly circular pattern, it means there is no strong bias in wind direction at Treasure Island. Converseley, dominant spokes represent favoured directions, and the more dark blue, the stronger the wind. Spokes point in the direction the wind blows from. Over an average northern hemisphere spring, the model suggests that winds are light enough for the sea to be glassy (the lightest shade of blue) about 55% of the time (50 days each northern hemisphere spring) and blows offshore 72% of the time (2 days in an average northern hemisphere spring). During a typical northern hemisphere spring winds exceeding >40kph (25mph) are not expected, but 0 have winds on the range 30-40 (19-25) at Treasure Island
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.