Iztapa Swell Statistics, Summer: All Swell – Any Wind
This image illustrates the range of swells directed at Iztapa through an average northern hemisphere summer and is based upon 5802 NWW3 model predictions since 2006 (values every 3 hours). The wave model does not forecast wind and surf right at the coast so we have chosen the most applicable grid node based on what we know about Iztapa, and at Iztapa the best grid node is 52 km away (32 miles).
The rose diagram illustrates 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 occurred only 0.1% of the time. Green and yellow show increasing swell sizes and largest swells greater than >3m (>10ft) are shown in red. In either graph, the area of any colour is proportional to how commonly that size swell occurs.
The diagram implies that the most common swell direction, shown by the longest spokes, was SSW, whereas the the most common wind blows from the E. Because the wave model grid is away from the coast, sometimes a strong offshore wind blows largest waves away from Iztapa and out to sea. We lump these in 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 Iztapa, 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 northern hemisphere summer, swells large enough to cause good for surfing waves at Iztapa 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.