Aln Estuary Swell Statistics, Summer: Surf with Light or Offshore Winds
This image shows only the swells directed at Aln Estuary that coincided with light winds or offshore conditions through a typical northern hemisphere summer. It is based on 7264 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 represents biggest 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 prevailing wind blows from the SW. 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 6% of the time, equivalent to 5 days. Open sea swells exceeding >3m (>10ft) are unlikely to arise in a normal northern hemisphere summer but 1.9% of the time we expect swell in the range 2-3m (6.5-10ft) 1.9%, equivalent to (2 days). Taking into account the proportion of these swells that coincided with predicted offshore winds, and given the fact that Aln Estuary is slightly protected from open water swells, we calculate that clean surf can be found at Aln Estuary about 6% of the time and that surf is blown out by onshore wind 5% of the time. This is means that we expect 10 days with waves in a typical northern hemisphere summer, of which 5 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.