This image shows only the swells directed at Democrat Point Robert Moses that coincided with light winds or offshore conditions through a typical northern hemisphere summer. It is based on 5066 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. Green and yellow illustrate increasing swell sizes and red shows the biggest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the most common swell direction, shown by the longest spokes, was SSE, whereas the the prevailing wind blows from the SW. 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 25% of the time, equivalent to 23 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal northern hemisphere summer but 1.7% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 1.7%, equivalent to (2 days). Taking into account the ratio of these swells that coincided with forecast offshore winds we think that that clean surf can be found at Democrat Point Robert Moses about 25% of the time and that surf is messed up by onshore wind 61% of the time. This is means that we expect 78 days with waves in a typical northern hemisphere summer, of which 23 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.