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Tahunanui bar Swell Statistics, March: All Swell – Any Wind

This chart shows the variation of swells directed at Tahunanui bar through a typical March, based on 2220 NWW3 model predictions since 2009 (values every 3 hours). The wave model does not forecast wind or surf right at the shore so we have chosen the most applicable grid node based on what we know about Tahunanui bar. In the case of Tahunanui bar, the best grid node is 36 km away (22 miles).

The rose diagram illustrates 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 were forecast 65% of the time. Green and yellow show increasing swell sizes and red illustrates the biggest 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 biggest spokes, was NNW, whereas the the prevailing wind blows from the WNW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Tahunanui bar and away from the coast. We lump these in with the no surf category of the bar chart. To simplify things we don't show these in the rose graph. Because wind determines whether or not waves are clean enough to surf at Tahunanui bar, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average March, swells large enough to cause surfable waves at Tahunanui bar run for about 7% 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.