Trecco Bay Swell Statistics, Spring: All Swell – Any Wind
This image describes the variation of swells directed at Trecco Bay through a typical northern hemisphere spring. It is based on 6002 NWW3 model predictions since 2007 (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 Trecco Bay, and at Trecco Bay 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 but without direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These happened 36% of the time. Green and yellow represent increasing swell sizes and red represents highest swells greater than >3m (>10ft). In either graph, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the dominant swell direction, shown by the largest spokes, was WSW, whereas the the dominant wind blows from the W. 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 clean enough to surf at Trecco Bay, you can load a different image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average northern hemisphere spring, swells large enough to cause surfable waves at Trecco Bay run for about 20% 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.