Trecco Bay Swell Statistics, Winter: All Swell – Any Wind
The rose diagram illustrates the variation of swells directed at Trecco Bay through a typical northern hemisphere winter. It is based on 6365 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind or surf right at the coast 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 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 occurred only 19% of the time. Green and yellow show increasing swell sizes and red represents the largest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how frequently that size swell happens.
The diagram suggests that the most common 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 offshore, sometimes a strong offshore wind blows largest waves away from Trecco Bay and away from the coast. We combine these with the no surf category of the bar chart. To keep it simple we don't show these in the rose diagram. Because wind determines whether or not waves are clean enough to surf at Trecco Bay, you can view an alternative image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. Over an average northern hemisphere winter, swells large enough to cause surfable 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.