Trecco Bay Swell Statistics, Spring: All Swell – Any Wind
The figure illustrates the variation of swells directed at Trecco Bay through a typical northern hemisphere spring and is based upon 6579 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coastline so we have chosen the best 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 sizes and swell direction, while the graph at the bottom shows the same thing but without direction information. Five colours represent increasing wave sizes. Very small swells of less than 0.5m (1.5 feet) high are shown in blue. These were forecast 35% of the time. Green and yellow show increasing swell sizes and largest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how commonly that size swell happens.
The diagram implies that the dominant swell direction, shown by the longest spokes, was WSW, whereas the the most common wind blows from the W. 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 group these with the no surf category of the bar chart. To simplify things we don't show these in the rose diagram. Because wind determines whether or not waves are good for surfing 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 clean enough to surf 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.