Porthcurno Swell Statistics, All Year: All Swell – Any Wind
This picture describes the variation of swells directed at Porthcurno over a normal year. It is based on 25437 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 most applicable grid node based on what we know about Porthcurno. In this particular case the best grid node is 13 km away (8 miles).
The rose diagram illustrates the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but 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 17% of the time. Green and yellow illustrate increasing swell sizes and red represents highest swells greater than >3m (>10ft). In each graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the most common swell direction, shown by the longest spokes, was WSW, whereas the the dominant wind blows from the W. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Porthcurno and offshore. We group these with the no surf category of the bar chart. To simplify things we don't show these in the rose graph. Because wind determines whether or not waves are good for surfing at Porthcurno, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. During a typical year, swells large enough to cause clean enough to surf waves at Porthcurno run for about 60% of the time.
IMPORTANT: Beta version feature! Swell heights are open water values from NWW3. There is no attempt to model near-shore effects. Coastal wave heights will generally be less, especially if the break does not have unobstructed exposure to the open ocean.