Hartley Reef Surf Stats

The graph shows the variation of swells directed at Hartley Reef through a typical September and is based upon 2880 NWW3 model predictions since 2008 (values every 3 hours). The wave model does not forecast wind or surf right at the shore so we have chosen the most applicable grid node based on what we know about Hartley Reef. In the case of Hartley Reef, the best grid node is 30 km away (19 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 occurred 56% of the time. Green and yellow show increasing swell sizes and red shows the biggest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell was forecast. The diagram implies that the dominant swell direction, shown by the biggest spokes, was NNE, whereas the the prevailing wind blows from the WSW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Hartley Reef and offshore. We combine 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 Hartley Reef, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average September, swells large enough to cause surfable waves at Hartley Reef run for about 14% of the time.

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