Lunar Semidiurnal Tide (M2)
This animation of the M2 tide may take a minute or two to load, during which time the frames will refresh one by one. When it is complete you will see the a continuous cycle from high tide (red) through zero (green) to low tide (blue), then back through zero to high tide again.
The M2 tide propagates around New Zealand at a fairly uniform speed, which you can see by following the red portion (high tide). Notice that when there is high tide on one side of Cook Strait, there is low tide on the other side. This means there is a 2m difference in M2 tide levels through the strait, explaining the large tidal currents which occur there. Click here to see currents through Cook Strait - 98KB animation.