In which direction is the mean flow through Cook Strait, New Zealand — evidence of 1 to 4 week variability?

Current‐meter observations at three sites in the narrows of Cook Strait over individual periods of 30–82 days confirm the dominance of the semi‐diurnal tidal flow. The major semi‐diurnal constituent, the M 2 tide, has near degenerate ellipses aligned through the Strait with amplitudes decreasing towards the west. Daily mean currents are dominated by flows with 2 and 4 weekly periods which are correlated with the wind (mainly the through Strait component) and possibly associated with the fortnightly MSf (4–9 cm s∼') and monthly Mm (4–7 cm s ‐1 ) tides (mainly the across Strait component). Mean currents over the observational periods were directed through the Strait, with a southward component at about 4cms ‐1 on the western side and a 5–14 cm s ‐1 northwards component on the eastern side. An appreciable (1–12 cm s ‐1 ) 6.2 hour M 4 tide is also present with flow directed mainly across Cook Strait. The Mm, MSf, and M 4 compound tides are probably associated with a response to interaction of the non‐linear field acceleration of the semi‐diurnal tide producing flow across the sloping sea floor.