Seaford Reef Swell Statistics, Autumn: All Swell – Any Wind
The figure shows the variation of swells directed at Seaford Reef through an average southern hemisphere autumn and is based upon 6580 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind and surf right at the shore so we have chosen the optimum grid node based on what we know about Seaford Reef. In this particular case the best grid node is 55 km away (34 miles).
The rose diagram shows 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 occurred only 87% of the time. Green and yellow represent increasing swell sizes and red shows the biggest swells, greater than >3m (>10ft). In each graph, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the dominant swell direction, shown by the longest spokes, was WSW, whereas the the prevailing wind blows from the SSE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Seaford Reef and away from the coast. We group these with the no surf category of the bar chart. To simplify things we don't show these in the rose plot. Because wind determines whether or not waves are surfable 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. In a typical southern hemisphere autumn, swells large enough to cause good for surfing 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.