Conditions at Katahama in December
December: Clean but Directionally Challenged
December ushers in the core winter pattern. The wind is overwhelmingly offshore - W (36.7%), WNW (25.9%), NW (4.8%), and NNW (3.9%) total 71.3% - making for glassy, groomed mornings on a regular basis. The problem is the swell direction: WNW (27.6%) and W (21.3%) dominate, and these are not the ideal directions for the ESE-facing beach. The optimal E/ESE/SE/SSE swell fraction drops to just 26.9%, and the average period shortens to 7.3s. As a result, there are many days when the bay looks clean but lacks proper shaped waves - the west swells either wrap inconsistently or are too short-period to draw crisp lines. The good news is that the occasional E/ESE swell can be spectacular under the strong offshore flow, creating clean, rippable 3-4ft (0.9-1.2m) surf. Air temperatures average 11.9°C, water drops to 17.3°C, and precipitation is low at 2.39 mm/day, so winter is dry and clear. A hooded 4/3 will keep you warm.
Average Spot conditions at Katahama in December
Swell history for December
Wind history for December
Swell quality
Analyze the groundswell consistency at Katahama during December. Based on historical data, there is a % probability of groundswell occurring this month. The chart below provides a detailed breakdown of the average wave height distribution, offering deep insights into the swell quality and surf potential you can expect at Katahama for your next trip in December.
Ground swell
Ground swell by size
Wind conditions
Evaluate the wind and swell alignment at Katahama for December. Our analysis shows that favorable offshore or side-shore winds coincide with surfable swell approximately % of the time. The accompanying graph illustrates the average size distribution of waves during these optimal wind windows at Katahama.