Ala Moana Swell Statistics, Summer: Surf with Light or Offshore Winds
This image shows only the swells directed at Ala Moana that coincided with light winds or offshore conditions over a normal southern hemisphere summer. It is based on 6931 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 show increasing swell sizes and red illustrates biggest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the prevailing swell direction, shown by the largest spokes, was SSW, whereas the the prevailing wind blows from the S. 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 11% of the time, equivalent to 10 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal southern hemisphere summer but 8% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 8%, equivalent to (7 days). Taking into account the ratio of these swells that coincided with forecast offshore winds, and given the fact that Ala Moana is exposed to open water swells, we estimate that clean surf can be found at Ala Moana about 11% of the time and that surf is messed up by onshore wind 87% of the time. This is means that we expect 89 days with waves in a typical southern hemisphere summer, 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.