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Gully's Swell Statistics, December: All Swell – Any Wind

The graph shows the variation of swells directed at Gully's over a normal December. It is based on 2953 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coast so we have chosen the best grid node based on what we know about Gully's, and at Gully's the best grid node is 46 km away (29 miles).

The rose diagram illustrates the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but lacks 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 0.8% of the time. Green and yellow represent increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In both graphs, 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 biggest spokes, was SSW, whereas the the prevailing wind blows from the NW. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Gully's and out to sea. We group these with the no surf category of the bar chart. To simplify things we don't show these in the rose plot. Because wind determines whether or not waves are good for surfing at Gully's, you can load a different image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. During a typical December, swells large enough to cause clean enough to surf waves at Gully's run for about 99% 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.