Aln Estuary Swell Statistics, April: Surf with Light or Offshore Winds
This image shows only the swells directed at Aln Estuary that coincided with light winds or offshore conditions over a normal April. It is based on 2160 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 represent increasing swell sizes and red represents largest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the prevailing swell direction, shown by the longest spokes, was NE, whereas the the most common wind blows from the SSW. 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 7% of the time, equivalent to 2 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal April but 5% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 5%, equivalent to (2 days). Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Aln Estuary is slightly protected from open water swells, we estimate that clean surf can be found at Aln Estuary about 7% of the time and that surf is messed up by onshore wind 12% of the time. This is means that we expect 6 days with waves in a typical April, of which 2 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.