Seaford Reef Swell Statistics, Autumn: All Swell – Any Wind
The figure describes the variation of swells directed at Seaford Reef through a typical southern hemisphere autumn, based on 6003 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind and surf right at the coast so we have chosen the optimum grid node based on what we know about Seaford Reef. In the case of Seaford Reef, the best grid node is 55 km away (34 miles).
The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but without direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These were forecast only 91% of the time. Green and yellow show increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how frequently that size swell was forecast.
The diagram suggests that the most common swell direction, shown by the longest spokes, was WSW, whereas the the dominant wind blows from the SSE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Seaford Reef and offshore. We group these 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 Seaford Reef, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average southern hemisphere autumn, swells large enough to cause surfable waves at Seaford Reef run for about 3% 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.