Assateague Swell Statistics, Spring: Surf with Light or Offshore Winds
This image shows only the swells directed at Assateague 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 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 illustrates biggest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how frequently that size swell was forecast.
The diagram suggests that the prevailing swell direction, shown by the biggest spokes, was SE, 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 28% of the time, equivalent to 25 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal northern hemisphere spring but 8% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 8%, equivalent to (7 days). Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Assateague is exposed to open water swells, we calculate that clean surf can be found at Assateague about 28% of the time and that surf is blown out by onshore wind 43% of the time. This is means that we expect 65 days with waves in a typical northern hemisphere spring, of which 25 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.