Otago Peninsula - Allans Beach Swell Statistics, Winter: Surf with Light or Offshore Winds
This image shows only the swells directed at Otago Peninsula - Allans Beach that coincided with light winds or offshore conditions over a normal southern hemisphere winter. It is based on 7266 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 represent 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 often that size swell happens.
The diagram indicates that the prevailing swell direction, shown by the largest spokes, was S, whereas the the most common wind blows from the WNW. 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 29% of the time, equivalent to 26 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal southern hemisphere winter but 3% of the time we expect swell in the range 2-3m (6.5-10ft) 3%, equivalent to (3 days). Taking into account the fraction of these swells that coincided with predicted offshore winds, and given the fact that Otago Peninsula - Allans Beach is exposed to open water swells, we calculate that clean surf can be found at Otago Peninsula - Allans Beach about 29% of the time and that surf is spoilt by onshore wind 39% of the time. This is means that we expect 62 days with waves in a typical southern hemisphere winter, of which 26 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.