The rose diagram shows only the swells directed at Long Beach that coincided with light winds or offshore conditions over a normal August. It is based on 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 show increasing swell sizes and red represents largest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the prevailing swell direction, shown by the longest spokes, was W (which was the same as the most common wind direction). 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 22% of the time, equivalent to 7 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal August but 11% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 11%, equivalent to (3 days). Taking into account the proportion of these swells that coincided with predicted offshore winds, and given the fact that Long Beach is exposed to open water swells, we estimate that clean surf can be found at Long Beach about 22% of the time and that surf is messed up by onshore wind 61% of the time. This is means that we expect 26 days with waves in a typical August, of which 7 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.