The rose diagram shows only the swells directed at Princeton Breakwater that coincided with light winds or offshore conditions through a typical July and is based upon 1736 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. Green and yellow illustrate increasing swell sizes and largest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the prevailing swell direction, shown by the largest spokes, was SW, whereas the the most common wind blows from the W. The chart at the bottom shows the same thing but without direction information. For example, swells larger than 1.5 feet (0.5m) coincided with good wind conditions 18% of the time, equivalent to 6 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal July but 8% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 8%, equivalent to (2 days). Taking into account the ratio of these swells that coincided with predicted offshore winds, and given the fact that Princeton Breakwater is exposed to open water swells, we think that that clean surf can be found at Princeton Breakwater about 18% of the time and that surf is spoilt by onshore wind 25% of the time. This is means that we expect 13 days with waves in a typical July, of which 6 days should be surfable.
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.