Auckland

Auckland sits on a narrow isthmus between two harbours on the upper North Island of New Zealand: the Waitematā opening east into the Hauraki Gulf and the Pacific, and the Manukau opening west into the Tasman Sea. That geography means the city has a tide on each side of itself, with different timing and slightly different range. The tide signature in the Waitematā is cleanly semidiurnal — two highs and two lows of comparable size, twelve and a half hours apart — with mean range at the Auckland ferry terminal about 2.5 metres climbing past 3.2 on spring tides and dropping near 1.6 on neaps. The Manukau on the west side runs a similar pattern but with high water reaching it about three hours later than the Waitematā, because the Tasman tide propagates around the top of the North Island via Cape Reinga. That east-vs-west offset is part of the local navigation lore for the harbour pilots and the Devonport ferry skippers. The Hauraki Gulf is dotted with islands — Rangitoto, Waiheke, Great Barrier, Little Barrier — and the tide changes the day for kayakers crossing to Rangitoto, snorkellers at Goat Island marine reserve, fishers on the Coromandel side, and yacht crews leaving the Viaduct for the gulf. Land Information New Zealand (LINZ) publishes the authoritative tide tables. The summer storm signal is mostly Tasman-Sea low pressure rather than tropical cyclone — surges of 20-40 cm above predicted are routine in winter.