Marina Swell Statistics, October: Surf with Light or Offshore Winds

This image shows only the swells directed at Marina that coincided with light winds or offshore conditions through a typical October. It is based on 2480 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 represent increasing swell sizes and biggest 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 was forecast.

The diagram implies that the dominant swell direction, shown by the biggest spokes, was WNW, whereas the the prevailing wind blows from the NW. 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 11 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal October but 13% of the time we expect swell in the range 2-3m (6.5-10ft) 13%, equivalent to (4 days). Taking into account the fraction of these swells that coincided with forecast offshore winds we estimate that clean surf can be found at Marina about 35% of the time and that surf is messed up by onshore wind 54% of the time. This is means that we expect 28 days with waves in a typical October, of which 11 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.