Batu Mandi Swell Statistics, February: All Swell – Any Wind
This chart describes the combination of swells directed at Batu Mandi through a typical February, based on 2032 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 optimum grid node based on what we know about Batu Mandi, and at Batu Mandi the best grid node is 35 km away (22 miles).
The rose diagram describes the distribution of swell directions and swell sizes, while the graph at the bottom shows the same thing but lacks direction information. Five colours show increasing wave sizes. The smallest swells, less than 0.5m (1.5 feet), high are coloured blue. These occurred only 9% of the time. Green and yellow represent 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 often that size swell happens.
The diagram indicates that the prevailing swell direction, shown by the longest spokes, was SSW, 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 Batu Mandi and away from the coast. We group these with the no surf category of the bar chart. To simplify things we don't show these in the rose plot. Because wind determines whether or not waves are clean enough to surf at Batu Mandi, you can select a similar diagram that shows only the swells that were forecast to coincide with glassy or offshore wind conditions. Over an average February, swells large enough to cause surfable waves at Batu Mandi run for about 91% 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.