Nahant Beach Swell Statistics, October: All Swell – Any Wind
The figure describes the combination of swells directed at Nahant Beach through an average October and is based upon 2231 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 best grid node based on what we know about Nahant Beach. In the case of Nahant Beach, the best grid node is 35 km away (22 miles).
The rose diagram shows the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but without direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These happened 48% of the time. Green and yellow represent increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the most common swell direction, shown by the largest spokes, was E, 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 Nahant Beach 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 graph. Because wind determines whether or not waves are surfable at Nahant Beach, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. In a typical October, swells large enough to cause good for surfing waves at Nahant Beach run for about 52% 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.