Ala Moana Swell Statistics, May: All Swell – Any Wind
This chart describes the combination of swells directed at Ala Moana through an average May, based on 2200 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind or surf right at the coastline so we have chosen the most applicable grid node based on what we know about Ala Moana. In this particular case the best grid node is 39 km away (24 miles).
The rose diagram describes the distribution of swell sizes and swell direction, while the graph at the bottom shows the same thing but 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 0% of the time. Green and yellow illustrate increasing swell sizes and red illustrates the highest swells, greater than >3m (>10ft). In either graph, 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 SSW, whereas the the dominant wind blows from the S. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Ala Moana 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 graph. Because wind determines whether or not waves are good for surfing at Ala Moana, you can load a different image that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. In a typical May, swells large enough to cause clean enough to surf waves at Ala Moana run for about 100% 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.