Aramoana Spit Swell Statistics, Autumn: Surf with Light or Offshore Winds
The rose diagram shows only the swells directed at Aramoana Spit that coincided with light winds or offshore conditions over a normal southern hemisphere autumn. It is based on 6580 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 largest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the prevailing swell direction, shown by the largest spokes, was ENE, whereas the the most common 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 6% of the time, equivalent to 5 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal southern hemisphere autumn but 5% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 5%, equivalent to (5 days). Taking into account the proportion of these swells that coincided with predicted offshore winds, and given the fact that Aramoana Spit is slightly protected from open water swells, we think that that clean surf can be found at Aramoana Spit about 6% of the time and that surf is messed up by onshore wind 10% of the time. This is means that we expect 15 days with waves in a typical southern hemisphere autumn, of which 5 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.