Trecco Bay Swell Statistics, Winter: All Swell – Any Wind
The figure illustrates the range of swells directed at Trecco Bay through a typical northern hemisphere winter, based on 6931 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 optimum grid node based on what we know about Trecco Bay. In this particular case the best grid node is 22 km away (14 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 show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These were forecast only 18% of the time. Green and yellow illustrate increasing swell sizes and largest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the prevailing swell direction, shown by the largest spokes, was WSW (which was the same as the most common wind direction). Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Trecco Bay and out to sea. 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 good for surfing at Trecco Bay, you can view an alternative image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average northern hemisphere winter, swells large enough to cause clean enough to surf waves at Trecco Bay run for about 49% 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.