Blackhead Surf Stats

This picture illustrates the variation of swells directed at Blackhead through a typical September. It is based on 3360 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the shore so we have chosen the best grid node based on what we know about Blackhead. In this particular case the best grid node is 35 km away (22 miles). The rose diagram illustrates the distribution of swell sizes and swell direction, 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 43% of the time. Green and yellow show increasing swell sizes and red represents largest 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 biggest spokes, was SE, whereas the the most common wind blows from the WNW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Blackhead 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 Blackhead, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average September, swells large enough to cause surfable waves at Blackhead run for about 57% of the time.

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