This picture describes the variation of swells directed at Taapuna through an average March, based on 1724 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coast so we have chosen the optimum grid node based on what we know about Taapuna, and at Taapuna the best grid node is 15 km away (9 miles).
The rose diagram illustrates the distribution of swell sizes and directions, while the graph at the bottom shows the same thing but without direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These happened only 18% of the time. Green and yellow show increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In each graph, the area of any colour is proportional to how commonly that size swell was forecast.
The diagram implies that the prevailing swell direction, shown by the largest spokes, was SSW, whereas the the dominant wind blows from the ENE. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Taapuna and offshore. We combine these with the no surf category of the bar chart. To keep it simple we don't show these in the rose diagram. Because wind determines whether or not waves are clean enough to surf at Taapuna, you can view an alternative image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. In a typical March, swells large enough to cause surfable waves at Taapuna run for about 82% 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.