A Street Swell Statistics, Winter: Surf with Light or Offshore Winds
The rose diagram shows only the swells directed at A Street 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 illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. Green and yellow illustrate increasing swell sizes and red illustrates the highest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the dominant swell direction, shown by the longest spokes, was SE, whereas the the dominant wind blows from the NW. 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 2.0% of the time, equivalent to 2 days. Open sea swells exceeding >3m (>10ft) are unlikely to happen in a normal northern hemisphere winter but 2% of the time you can expect swell in the range 1.3-2m (4-6.5ft) 2%, equivalent to (2 days). Taking into account the fraction of these swells that coincided with forecast offshore winds, and given the fact that A Street is slightly protected from open water swells, we think that that clean surf can be found at A Street about 2.0% of the time and that surf is spoilt by onshore wind 2.0% of the time. This is means that we expect 4 days with waves in a typical northern hemisphere winter, 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.