Agate and Pearl Street Swell Statistics, December: Surf with Light or Offshore Winds
This image shows only the swells directed at Agate and Pearl Street that coincided with light winds or offshore conditions through a typical December. It is based on 2457 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 show increasing swell sizes and red represents largest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the most common swell direction, shown by the biggest spokes, was WSW, whereas the the most common wind blows from the NNW. 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 39% of the time, equivalent to 12 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal December. Taking into account the ratio of these swells that coincided with predicted offshore winds, and given the fact that Agate and Pearl Street is exposed to open water swells, we estimate that clean surf can be found at Agate and Pearl Street about 39% of the time and that surf is blown out by onshore wind 24% of the time. This is means that we expect 19 days with waves in a typical December, of which 12 days should be clean enough to surf.
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.