St Marys Rivermouth Surf Stats

The graph describes the range of swells directed at St Marys Rivermouth through an average July, based on 3472 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the optimum grid node based on what we know about St Marys Rivermouth. In this particular case the best grid node is 47 km away (29 miles). The rose diagram describes the distribution of swell sizes and directions, while the graph at the bottom shows the same thing 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 happened 25% of the time. Green and yellow illustrate increasing swell sizes and red illustrates the highest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how commonly that size swell occurs. The diagram implies that the dominant swell direction, shown by the largest spokes, was E, whereas the the dominant wind blows from the S. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from St Marys Rivermouth and out to sea. 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 clean enough to surf at St Marys Rivermouth, you can view an alternative image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. In a typical July, swells large enough to cause surfable waves at St Marys Rivermouth run for about 75% of the time.

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