Airport Lefts Swell Statistics, Spring: Surf with Light or Offshore Winds
This image shows only the swells directed at Airport Lefts that coincided with light winds or offshore conditions through a typical southern hemisphere spring. It is based on 7252 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 illustrate increasing swell sizes and highest 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 occurs.
The diagram implies that the prevailing swell direction, shown by the largest spokes, was SW, whereas the the dominant wind blows from the SSE. 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 68% of the time, equivalent to 62 days. Open water swells exceeding >3m (>10ft) only happen 0.8% of the time in a typical southern hemisphere spring, equivalent to just one day but 33% of the time we expect swell in the range 2-3m (6.5-10ft) 33%, equivalent to (30 days). Taking into account the fraction of these swells that coincided with predicted offshore winds, and given the fact that Airport Lefts is exposed to open water swells, we think that that clean surf can be found at Airport Lefts about 68% of the time and that surf is blown out by onshore wind 32% of the time. This is means that we expect 91 days with waves in a typical southern hemisphere spring, of which 62 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.