Ahu Ahu Road Swell Statistics, Spring: All Swell – Any Wind
The figure describes the variation of swells directed at Ahu Ahu Road through an average southern hemisphere spring, based on 7252 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coastline so we have chosen the most applicable grid node based on what we know about Ahu Ahu Road. In the case of Ahu Ahu Road, the best grid node is 17 km away (11 miles).
The rose diagram describes the distribution of swell directions and swell sizes, 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 7% of the time. Green and yellow show increasing swell sizes and highest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how often that size swell happens.
The diagram indicates that the dominant swell direction, shown by the largest spokes, was WSW, whereas the the dominant wind blows from the W. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Ahu Ahu Road and away from the coast. We combine these with the no surf category of the bar chart. To keep it simple we don't show these in the rose plot. Because wind determines whether or not waves are surfable at Ahu Ahu Road, 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 southern hemisphere spring, swells large enough to cause good for surfing waves at Ahu Ahu Road run for about 93% 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.