Conditions at Katahama in September
September: Maximum Swell Window, But Wind Fights Back
September is the start of the autumn transition and the single highest month for optimal swell direction at Katahama. E (13.4%), ESE (19.7%), SE (17.0%), and SSE (14.1%) combine for an outstanding 64.2% of all swell, and the average period remains long at 9.2s. The average swell height also peaks at 1.4m (4.5ft). However, the wind pattern is wretchedly onshore: ENE (23.3%) and E (14.9%) are the leading directions, with NE (11.1%) and WSW (10.3%) also blowing against the surf quality. Offshore flow from the west/northwest is only 10.5%. This makes September all about the typhoon passage - when a storm approaches or lingers to the south, the ESE/SE groundswell arrives with plenty of size and period, but the accompanying northeasterly winds can turn the lineup into a washing machine. The few days where the typhoon axis shifts far enough away to allow W/NW winds are the absolute best of the year. Expect warm water (25.7°C), air temps around 25.0°C, and abundant rainfall (7.98 mm/day).
Average Spot conditions at Katahama in September
Swell history for September
Wind history for September
Swell quality
Analyze the groundswell consistency at Katahama during September. 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 September.
Ground swell
Ground swell by size
Wind conditions
Evaluate the wind and swell alignment at Katahama for September. 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.