Aramoana Spit Swell Statistics, March: All Swell – Any Wind
The graph shows the combination of swells directed at Aramoana Spit through a typical March and is based upon 2220 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 optimum grid node based on what we know about Aramoana Spit. In this particular case the best grid node is 29 km away (18 miles).
The rose diagram describes the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but lacks direction information. Five colours illustrate increasing wave sizes. Blue shows the smallest swells, less that 0.5m (1.5 feet) high. These were forecast only 77% of the time. Green and yellow illustrate increasing swell sizes and red shows the biggest swells, greater than >3m (>10ft). In either graph, the area of any colour is proportional to how frequently that size swell occurs.
The diagram suggests that the prevailing swell direction, shown by the biggest spokes, was ENE, 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 Aramoana Spit and out to sea. We lump these in 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 clean enough to surf at Aramoana Spit, you can select a similar diagram that shows only the swells that were expected to coincide with glassy or offshore wind conditions. Over an average March, swells large enough to cause surfable waves at Aramoana Spit run for about 13% 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.