Groenvlei Surf Stats

The figure illustrates the combination of swells directed at Groenvlei through an average July and is based upon 3472 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the best grid node based on what we know about Groenvlei. In this particular case the best grid node is 56 km away (35 miles). The rose diagram describes the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing 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 4% of the time. Green and yellow illustrate increasing swell sizes and red shows largest swells greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell happens. The diagram implies that the most common swell direction, shown by the biggest spokes, was SSW, whereas the the most common wind blows from the W. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Groenvlei 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 surfable at Groenvlei, you can load a different image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical July, swells large enough to cause good for surfing waves at Groenvlei run for about 96% of the time.

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