Trial Harbour Swell Statistics, Autumn: All Swell – Any Wind
This picture illustrates the range of swells directed at Trial Harbour through an average southern hemisphere autumn. It is based on 5140 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the most applicable grid node based on what we know about Trial Harbour. In this particular case the best grid node is 16 km away (10 miles).
The rose diagram illustrates the distribution of swell sizes and directions, 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 0.3% of the time. Green and yellow show increasing swell sizes and red illustrates largest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how frequently that size swell happens.
The diagram suggests that the most common swell direction, shown by the longest spokes, was SW, whereas the the most common wind blows from the WNW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Trial Harbour 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 plot. Because wind determines whether or not waves are good for surfing at Trial Harbour, you can load a different image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical southern hemisphere autumn, swells large enough to cause clean enough to surf waves at Trial Harbour run for about 100% 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.