Army Beach Swell Statistics, Setembro: Surf with Light or Offshore Winds
This image shows only the swells directed at Army Beach that coincided with light winds or offshore conditions through a typical September and is based upon 2400 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 illustrates biggest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how frequently that size swell was forecast.
The diagram suggests that the most common swell direction, shown by the largest spokes, was NNW, whereas the the prevailing 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 6% of the time, equivalent to 2 days. Open sea swells exceeding >3m (>10ft) are unlikely to occur in a normal September. Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that Army Beach is exposed to open water swells, we calculate that clean surf can be found at Army Beach about 6% of the time and that surf is messed up by onshore wind 29% of the time. This is means that we expect 10 days with waves in a typical September, 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.