Ala Moana Bowls Swell Statistics, September: Surf with Light or Offshore Winds
This image shows only the swells directed at Ala Moana Bowls that coincided with light winds or offshore conditions through a typical September. It is based on 2400 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 illustrates the biggest swells, greater than >3m (>10ft). In each 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 longest spokes, was S, whereas the the prevailing wind blows from the ENE. 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 19% of the time, equivalent to 6 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal September but 7% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 7%, equivalent to (2 days). Taking into account the ratio of these swells that coincided with expected offshore winds, and given the fact that Ala Moana Bowls is exposed to open water swells, we calculate that clean surf can be found at Ala Moana Bowls about 19% of the time and that surf is spoilt by onshore wind 33% of the time. This is means that we expect 16 days with waves in a typical September, of which 6 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.