Kōchi tide times

Kōchi is the capital of Kōchi Prefecture on Shikoku's Pacific coast, built on a flat river delta at the head of Tosa Bay — a wide, deep embayment opening south into the Pacific. The city is separated from the Seto Inland Sea side of Shikoku by the Shikoku Mountains. The Pacific orientation defines everything here: direct swell exposure, high typhoon frequency, and an open-ocean tidal regime.

The tidal regime at Kōchi is semidiurnal with a spring range of approximately 2.0 m above Chart Datum. Mean high water springs is around 1.5 m; mean low water springs around 0.5 m. Neap range narrows to 0.8–1.0 m. Tosa Bay swell climate is one of the most exposed in Japan: southerly Pacific swell reaches the bay with minimal attenuation and can run to 4–5 m at the outer headlands in typhoon conditions.

For the offshore fishery, Kōchi is Japan's most important tuna and bonito port. The skip-jack tuna (katsuo) one-pole fishery operated from Kōchi has been the economic base of the coastal culture here for centuries. Katsuo no tataki — flame-grilled bonito with garlic and ginger — is Kōchi's signature dish. The offshore fishing grounds in the Kuroshio Current south of Tosa Bay are among the richest in Japan; tidal state is secondary to the Kuroshio's meanders and the seasonal katsuo migration for offshore boats.

For inshore anglers, Tosa Bay's 2.0 m spring range creates productive tidal flat conditions at river mouths. The Kokubu River mouth at the eastern edge of the city is a traditional mullet and sea bass (suzuki) fishery; bass enter the estuary on the flooding tide and are fished from the river-mouth bank. The flooding window — 1–2 hours before to 1 hour after high water — is the productive period.

Surfers use the outer beaches east and west of the city — Katsurahama (6 km south) and beaches near Aki and Tosa City — for Pacific swell. Swell of 1.0–2.0 m is common October through March; typhoon swells reach 4–6 m at the outer point breaks. Tidal state matters at the rocky reef breaks: on a 2.0 m spring range, the difference between high and low water at a shallow reef break is the difference between rideable wave and closed-out shore pound. Most reef breaks work best on the middle portion of the tide — the upper half of the ebb.

Katsurahama Beach, 6 km south, is the most photographed beach in Kōchi Prefecture: a curved cove below the cliffs with a bronze statue of samurai hero Sakamoto Ryōma at the clifftop. The beach is not safe for swimming due to Pacific shore-break and rip currents, but the 2.0 m tidal range provides photographers with a broad sandy foreground at low water and a wave-at-the-rocks composition at high water.

Typhoon season runs July through October. Direct hits on Kōchi are more frequent than on most of Japan's Pacific coastline. A direct-hit storm surge of 2–4 m arriving at spring high water (1.5 m above Chart Datum) creates total water levels of 3.5–5.5 m above Chart Datum in the low-lying delta areas of the city.

All tide predictions for Kōchi come from the Open-Meteo Marine gridded model. Timing accuracy is ±45 minutes; height accuracy is ±0.3 m above Chart Datum.