Ackergill Swell Statistics, February: All Swell – Any Wind
The figure describes the variation of swells directed at Ackergill through an average February and is based upon 2102 NWW3 model predictions since 2007 (values every 3 hours). The wave model does not forecast surf and wind right at the coast so we have chosen the most applicable grid node based on what we know about Ackergill. In this particular case the best grid node is 5 km away (3 miles).
The rose diagram shows the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing 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 were forecast only 80% of the time. Green and yellow show increasing swell sizes and red shows the highest swells, greater than >3m (>10ft). In both graphs, the area of any colour is proportional to how frequently that size swell was forecast.
The diagram suggests that the most common swell direction, shown by the longest spokes, was N, whereas the the dominant wind blows from the SW. Because the wave model grid is out to sea, sometimes a strong offshore wind blows largest waves away from Ackergill 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 clean enough to surf at Ackergill, 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 February, swells large enough to cause surfable waves at Ackergill run for about 20% 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.