The Trough Swell Statistics, December: All Swell – Any Wind
The graph describes the variation of swells directed at The Trough over a normal December, based on 1961 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the most applicable grid node based on what we know about The Trough, and at The Trough the best grid node is 52 km away (32 miles).
The rose diagram describes the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but lacks direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These happened only 92% of the time. Green and yellow show 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 commonly that size swell happens.
The diagram implies that the prevailing swell direction, shown by the largest spokes, was WSW, whereas the the dominant wind blows from the S. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from The Trough and away from the coast. We lump these in with the no surf category of the bar chart. To avoid confusion we don't show these in the rose graph. Because wind determines whether or not waves are clean enough to surf at The Trough, you can select a similar diagram that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical December, swells large enough to cause surfable waves at The Trough run for about 4% of the time.
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.