Manly Swell Statistics, Autumn: All Swell – Any Wind
The graph illustrates the range of swells directed at Manly through an average southern hemisphere autumn. It is based on 5786 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 most applicable grid node based on what we know about Manly, and at Manly the best grid node is 29 km away (18 miles).
The rose diagram shows the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but without direction information. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These occurred only 18% of the time. Green and yellow represent increasing swell sizes and red illustrates largest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the most common swell direction, shown by the largest spokes, was SE, whereas the the most common wind blows from the SSW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Manly and away from the coast. We combine these with the no surf category of the bar chart. To keep it simple we don't show these in the rose diagram. Because wind determines whether or not waves are surfable at Manly, you can view an alternative 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 good for surfing waves at Manly run for about 28% 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.