Army Beach Swell Statistics, Winter: Surf with Light or Offshore Winds
This image shows only the swells directed at Army Beach that coincided with light winds or offshore conditions over a normal northern hemisphere winter. It is based on 6931 predictions, one every 3 hours. The direction of the spokes show where quality surf generating swell comes from. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. Green and yellow represent increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the prevailing swell direction, shown by the longest spokes, was NNW, 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 29% of the time, equivalent to 26 days. Open water swells exceeding >3m (>10ft) only happen 1.3% of the time in a typical northern hemisphere winter, equivalent to just one day but 13% of the time we expect swell in the range 2-3m (6.5-10ft) 13%, equivalent to (12 days). Taking into account the proportion of these swells that coincided with predicted 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 29% of the time and that surf is spoilt by onshore wind 54% of the time. This is means that we expect 76 days with waves in a typical northern hemisphere winter, of which 26 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.