Avalanche Swell Statistics, Spring: Surf with Light or Offshore Winds
This image shows only the swells directed at Avalanche that coincided with light winds or offshore conditions over a normal 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 illustrate increasing swell sizes and red illustrates largest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the most common swell direction, shown by the biggest spokes, was NW, whereas the the most common 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 39% of the time, equivalent to 35 days. Open water swells exceeding >3m (>10ft) only happen 0.7% of the time in a typical northern hemisphere spring, 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 forecast offshore winds, and given the fact that Avalanche is exposed to open water swells, we estimate that clean surf can be found at Avalanche about 39% of the time and that surf is blown out by onshore wind 15% of the time. This is means that we expect 49 days with waves in a typical northern hemisphere spring, of which 35 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.