Assateague Swell Statistics, Setembro: 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 September. It is based on 2400 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 highest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the prevailing swell direction, shown by the largest spokes, was SE, whereas the the dominant wind blows from the ENE. 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 30% of the time, equivalent to 9 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal September. Taking into account the proportion of these swells that coincided with expected 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 30% of the time and that surf is messed up by onshore wind 55% of the time. This is means that we expect 26 days with waves in a typical September, of which 9 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.