Kantō (Tokyo Bay)

The Kantō region wraps the head of Tokyo Bay on Japan's Pacific coast, with Tokyo on the inner shore, Yokohama and Kawasaki on the western, Chiba and the Bōsō Peninsula on the eastern, and the narrow Uraga Channel opening south to Sagami Bay and the open Pacific. The tide signature here is a moderate mixed-semidiurnal signal — two highs and two lows of unequal size each day, the bigger swing falling on the lower-low water, with the pattern shifting toward strongly diurnal at certain points in the lunar month. Mean range at Tokyo's Harumi gauge is about 1.3 metres, climbing past 2.0 metres on the largest spring tides and dropping near 0.6 on neaps. The bay itself behaves as a partially-enclosed basin connected to the Pacific through the 7 km Uraga Channel between Yokosuka and the Bōsō Peninsula; tidal currents through that throat exceed two knots on the change of tide and concentrate sharper than the height swing implies. Tsukiji and now Toyosu's wholesale fish operations, the dredged container approaches at Yokohama and Kawasaki, the working sailors at Hayama and the Miura Peninsula, and the long sand at Kujūkuri on the Bōsō outer coast all read the table for different windows. Edomae fishing tradition — the small-boat inshore catch that fed Edo and built the Tokyo sushi style — turned on tide timing, and the rhythm survives in the tsukudani salt-cooked seafood industry on the bay shore. The Japan Meteorological Agency and the Japan Coast Guard Hydrographic and Oceanographic Department publish authoritative tide tables. Typhoon-season surge from late summer and autumn cyclones can lift levels well above predicted.