St Ives Harbour Wall Surf Stats

The rose diagram illustrates the range of swells directed at St Ives Harbour Wall over a normal April and is based upon 3360 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coastline so we have chosen the optimum grid node based on what we know about St Ives Harbour Wall. In this particular case the best grid node is 32 km away (20 miles). The rose diagram illustrates 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 15% of the time. Green and yellow show increasing swell sizes and red shows the largest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how often that size swell was forecast. The diagram indicates that the prevailing swell direction, shown by the longest spokes, was W, whereas the the most common wind blows from the NNE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from St Ives Harbour Wall and offshore. We lump these in 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 good for surfing at St Ives Harbour Wall, you can view an alternative image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical April, swells large enough to cause clean enough to surf waves at St Ives Harbour Wall run for about 23% of the time.

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