Pirangi Reef Surf Stats

The rose diagram describes the combination of swells directed at Pirangi Reef through a typical April, based on 3120 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coastline so we have chosen the best grid node based on what we know about Pirangi Reef. In the case of Pirangi Reef, the best grid node is 12 km away (7 miles). The rose diagram illustrates the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These were forecast only 8% of the time. Green and yellow represent increasing swell sizes and red shows highest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell occurs. The diagram implies that the dominant swell direction, shown by the largest spokes, was NE, whereas the the dominant wind blows from the ESE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Pirangi Reef and away from the coast. We group these 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 clean enough to surf at Pirangi 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 April, swells large enough to cause surfable waves at Pirangi Reef run for about 92% of the time.

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