Asu Swell Statistics, Spring: Surf with Light or Offshore Winds
This image shows only the swells directed at Asu that coincided with light winds or offshore conditions through a typical northern hemisphere spring. 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 show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. Green and yellow show 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 commonly that size swell occurs.
The diagram implies that the most common swell direction, shown by the longest spokes, was SSW, whereas the the most common 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 66% of the time, equivalent to 60 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal northern hemisphere spring but 7% of the time we expect swell in the range 2-3m (6.5-10ft) 7%, equivalent to (6 days). Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Asu is exposed to open water swells, we think that that clean surf can be found at Asu about 66% of the time and that surf is blown out by onshore wind 34% of the time. This is means that we expect 91 days with waves in a typical northern hemisphere spring, of which 60 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.