Asu Swell Statistics, April: 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 April and is based upon 2160 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 red represents the highest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the most common swell direction, shown by the longest spokes, was SSW, whereas the the dominant wind blows from the W. 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 65% of the time, equivalent to 20 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal April but 42% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 42%, equivalent to (13 days). Taking into account the fraction of these swells that coincided with predicted 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 65% of the time and that surf is blown out by onshore wind 35% of the time. This is means that we expect 30 days with waves in a typical April, of which 20 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.