Aberystwyth harbour trap Swell Statistics, Abril: Surf with Light or Offshore Winds
This image shows only the swells directed at Aberystwyth harbour trap 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 illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. Green and yellow show increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the most common swell direction, shown by the largest spokes, was SW, 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 1.2% of the time, equivalent to 0 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal April. Taking into account the fraction of these swells that coincided with predicted offshore winds, and given the fact that Aberystwyth harbour trap is slightly protected from open water swells, we calculate that clean surf can be found at Aberystwyth harbour trap about 1.2% of the time and that surf is messed up by onshore wind 10% of the time. This is means that we expect 3 days with waves in a typical April, of which 0 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.