Trecco Bay Swell Statistics, Winter: All Swell – Any Wind
The rose diagram describes the variation of swells directed at Trecco Bay through an average northern hemisphere winter, based on 6365 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, and at Trecco Bay the best grid node is 22 km away (14 miles).
The rose diagram describes the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These occurred only 19% of the time. Green and yellow illustrate increasing swell sizes and red represents highest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the prevailing swell direction, shown by the longest spokes, was WSW (which was the same as the dominant wind direction). Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Trecco Bay 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 plot. Because wind determines whether or not waves are surfable at Trecco Bay, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. In a typical northern hemisphere winter, swells large enough to cause good for surfing waves at Trecco Bay run for about 46% 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.