This image shows only the swells directed at Long Beach that coincided with light winds or offshore conditions over a normal December. 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 show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. Green and yellow represent increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the prevailing swell direction, shown by the largest spokes, was W, whereas the the prevailing wind blows from the ESE. 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 35% of the time, equivalent to 10 days. Expect open water swells to exceed >3m (>10ft) 6% of the time (2 days). Taking into account the ratio of these swells that coincided with expected 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 35% of the time and that surf is spoilt by onshore wind 54% of the time. This is means that we expect 27 days with waves in a typical December, of which 10 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.