Ann Street Peaks Swell Statistics, Autumn: Surf with Light or Offshore Winds
The rose diagram shows only the swells directed at Ann Street Peaks that coincided with light winds or offshore conditions over a normal southern hemisphere autumn and is based upon 6580 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 represent increasing swell sizes and red represents the biggest swells, greater than >3m (>10ft). In either 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 biggest spokes, was ESE, whereas the the prevailing wind blows from the SE. 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 18% of the time, equivalent to 16 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal southern hemisphere autumn but 6% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 6%, equivalent to (5 days). Taking into account the fraction of these swells that coincided with predicted offshore winds, and given the fact that Ann Street Peaks is exposed to open water swells, we calculate that clean surf can be found at Ann Street Peaks about 18% of the time and that surf is blown out by onshore wind 78% of the time. This is means that we expect 87 days with waves in a typical southern hemisphere autumn, of which 16 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.