Asu Swell Statistics, Summer: Surf with Light or Offshore Winds
This image shows only the swells directed at Asu that coincided with light winds or offshore conditions over a normal northern hemisphere summer. 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 represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. Green and yellow illustrate increasing swell sizes and red illustrates biggest swells greater than >3m (>10ft). In both graphs, 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 WSW. 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 71% of the time, equivalent to 65 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal northern hemisphere summer but 27% of the time we expect swell in the range 2-3m (6.5-10ft) 27%, equivalent to (25 days). Taking into account the fraction of these swells that coincided with expected offshore winds, and given the fact that Asu is exposed to open water swells, we calculate that clean surf can be found at Asu about 71% of the time and that surf is blown out by onshore wind 29% of the time. This is means that we expect 91 days with waves in a typical northern hemisphere summer, of which 65 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.