Tokyo Bay (Harumi) tide times

The hero block shows the next high tide at the Harumi gauge in central Tokyo Bay in local Japan Standard Time (UTC+9, no DST). The 7-day table covers all the highs and lows. High water at Yokohama on the western shore lags Harumi by a few minutes; at the bay mouth in the Uraga Channel it leads by about half an hour.

Mean range at the Harumi gauge is about 1.3 metres, climbing past 2 metres on the largest spring tides and dropping near 0.6 metres on neaps. The pattern is mixed semidiurnal — two highs and two lows of unequal size most days, with the biggest swing falling on the lower-low water — and shifts toward strongly diurnal at certain points in the lunar month.

Open-Meteo Marine, a gridded global ocean model. Useful for daily planning around the bay, the Uraga Channel, and the Bōsō outer coast. For authoritative Japanese tide data, the Japan Meteorological Agency and the Japan Coast Guard Hydrographic and Oceanographic Department publish the official tide tables and operate the reference gauge network.

The Uraga Channel is the narrow 7-kilometre throat connecting the bay to the open Pacific, between Yokosuka and the Bōsō Peninsula. Tidal currents through that throat exceed two knots on the change of tide because the entire bay's water exchanges through that single bottleneck. The container pilots running the deep-water approaches at Yokohama and the JMS naval traffic out of Yokosuka all time their transits to slack water on the rising flood.

No. For piloting in or out of Tokyo Bay, transiting the Uraga Channel, or working the Bōsō outer coast use the Japan Coast Guard's authoritative tide tables, the JMA marine forecasts, and the Tokyo Bay Vessel Traffic Service guidance. Typhoon-season surge from late summer and autumn cyclones can lift levels well above predicted, and tsunami advisories override everything.