Washington

Washington's tidal coast is dominated by Puget Sound, the long inland sea connected to the Pacific via the Strait of Juan de Fuca. The tide here is amplified mixed semidiurnal: mean range at Seattle's Pier 36 gauge is about 2.3 metres, with the lower low and the higher high of a typical summer day separated by three metres or more. Two highs and two lows fall each day, but the asymmetry is sharp — the morning low and evening low can differ by a metre, and the same for the highs. That changes the day for waterfront walkers, paddlers out of Alki, and anyone watching boats lock through Ballard. Lowest lows around new and full moons, especially in summer afternoons, pull water off the inner-shelf flats at Lincoln Park and Discovery Park, opening rocky intertidal that stays covered the rest of the month. South-wind storm surge in winter can lift levels 20–30 cm above predicted, sometimes more. NOAA CO-OPS runs the harmonic predictions; the Tacoma Narrows and Deception Pass currents are some of the strongest in the lower 48 and reward real-time pilotage.