Shelter Island Surf Stats

The rose diagram shows the combination of swells directed at Shelter Island through an average April and is based upon 3360 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the shore so we have chosen the best grid node based on what we know about Shelter Island. In this particular case the best grid node is 28 km away (17 miles). The rose diagram shows the distribution of swell sizes and swell direction, 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 occurred only 83% of the time. Green and yellow show increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how often that size swell happens. The diagram indicates that the dominant swell direction, shown by the largest spokes, was ENE, whereas the the prevailing wind blows from the ESE. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Shelter Island and away from the coast. We lump these in with the no surf category of the bar chart. To avoid confusion we don't show these in the rose diagram. Because wind determines whether or not waves are good for surfing at Shelter Island, you can load a different image that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical April, swells large enough to cause clean enough to surf waves at Shelter Island run for about -1% of the time.

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