Porthleven Surf Stats

The rose diagram illustrates the combination of swells directed at Porthleven over a normal June, based on 3506 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the most applicable grid node based on what we know about Porthleven. In this particular case the best grid node is 15 km away (9 miles). The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but lacks 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 16% of the time. Green and yellow show increasing swell sizes and red shows largest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell was forecast. The diagram implies that the prevailing swell direction, shown by the longest spokes, was WSW, 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 Porthleven and offshore. We group these with the no surf category of the bar chart. To keep it simple we don't show these in the rose graph. Because wind determines whether or not waves are surfable at Porthleven, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. During a typical June, swells large enough to cause good for surfing waves at Porthleven run for about 84% of the time.

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