The rose diagram illustrates how often and how strongly the wind blows from different directions over a normal northern hemisphere summer. The biggest 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 5066 NWW3 forecasts of wind since since 2006, at 3hr intervals, for the closest NWW3 model node to 21st Street (Miami), located 26 km away (16 miles). There are too few recording stations world wide to use actual wind data. Without question some coastal places have very localized wind effects that would not be predicted by NWW3.
According to the model, the prevailing wind at 21st Street (Miami) blows from the NE. If the rose graph shows a fairly circular pattern, it means there is no strong bias in wind direction at 21st Street (Miami). By contrast, dominant spokes illustrate favoured directions, and the more deep blue, the stronger the wind. Spokes point in the direction the wind blows from. During a typical northern hemisphere summer, the model suggests that winds are light enough for the sea to be glassy (pale blue) about 10% of the time (9 days each northern hemisphere summer) and blows offshore 13% of the time (0 days in an average northern hemisphere summer). Over an average northern hemisphere summer winds exceeding >40kph (25mph) are not expected, but 1 have winds on the range 30-40 (19-25) at 21st Street (Miami)
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.