Katsunan Ko — marine weather & port guide
Katsunan Ko is a port in Japan at 35°40.0′N 139°59.0′E. Today (Aug 3): S wind 1–4 kn, waves 3.6–4.0 m, from the ECMWF IFS run 2026-08-03 12z. The live chart on this page shows current conditions and plans weather-optimized departures from this harbor.
Port facts (NGA World Port Index)| Position | 35°40.0′N 139°59.0′E |
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| Harbor size | Small |
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| Harbor type | Coastal breakwater harbor |
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| Shelter | Good |
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| Channel depth | 11 m |
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| Anchorage depth | 14 m |
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| Tide range | 9 m |
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| Pilotage | Compulsory |
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| Time zone | Asia/Tokyo |
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10-day marine forecast — Katsunan Ko
| Date | Wind | Gusts | Waves |
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| S 1–4 kn | 8 kn | 3.6–4.0 m |
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| SSE 0–4 kn | 13 kn | 3.8–4.1 m |
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| SSW 2–5 kn | 14 kn | 2.8–3.6 m |
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| SSW 2–5 kn | 13 kn | 2.4–2.7 m |
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| SW 2–5 kn | 15 kn | 2.2–2.3 m |
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| NW 1–3 kn | 4 kn | 2.0–2.1 m |
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| ENE 2–3 kn | 4 kn | 2.1–2.2 m |
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| S 1–1 kn | 10 kn | 3.0–3.0 m |
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| S 2–2 kn | 11 kn | 1.8–1.8 m |
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| SSE 2–2 kn | 9 kn | 1.5–1.5 m |
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Forecast from the ECMWF IFS model run , waves from ECMWF WAM. Updated with each model cycle; the live chart below recalculates for your departure time and vessel.
Frequently asked
How is the weather at Katsunan Ko right now?
As of the ECMWF IFS run 2026-08-03 12z: S wind 1–4 kn, waves 3.6–4.0 m. The 10-day outlook is in the forecast table on this page and updates with each model cycle.
How big is the harbor at Katsunan Ko?
Katsunan Ko is classed as a small harbor (coastal breakwater harbor), with good shelter in the NGA World Port Index.
How deep is the approach to Katsunan Ko?
Per the NGA World Port Index, the entrance channel carries about 11 m and anchorage depths run about 14 m. Verify against current official charts before entry.