Llangennith Swell Statistics, April: All Swell – Any Wind
This picture shows the combination of swells directed at Llangennith through a typical April and is based upon 1680 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast wind and surf right at the shore so we have chosen the most applicable grid node based on what we know about Llangennith. In this particular case the best grid node is 17 km away (11 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 happened 31% of the time. Green and yellow show increasing swell sizes and biggest swells greater than >3m (>10ft) are shown in red. In both graphs, the area of any colour is proportional to how often that size swell occurs.
The diagram indicates that the most common swell direction, shown by the largest spokes, was WSW, whereas the the prevailing wind blows from the NW. Because the wave model grid is offshore, sometimes a strong offshore wind blows largest waves away from Llangennith and away from the coast. We combine these with the no surf category of the bar chart. To avoid confusion we don't show these in the rose diagram. Because wind determines whether or not waves are clean enough to surf at Llangennith, you can view an alternative image that shows only the swells that were predicted to coincide with glassy or offshore wind conditions. Over an average April, swells large enough to cause surfable waves at Llangennith run for about 69% 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.