Avalanche Swell Statistics, December: Surf with Light or Offshore Winds
The rose diagram shows only the swells directed at Avalanche that coincided with light winds or offshore conditions over a normal December and is based upon 2457 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 show increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In either 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 biggest spokes, was W, whereas the the prevailing wind blows from the S. 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 34% of the time, equivalent to 10 days. Expect open water swells to exceed >3m (>10ft) 6% of the time (2 days). Taking into account the ratio of these swells that coincided with forecast offshore winds, and given the fact that Avalanche is exposed to open water swells, we think that that clean surf can be found at Avalanche about 34% of the time and that surf is messed up by onshore wind 63% of the time. This is means that we expect 29 days with waves in a typical December, of which 10 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.