TIDES are a consequence of the gravitational attraction of the earth to both the moon and the sun with the moon generally being more than twice as strong as the sun because it is so much closer to the earth. The moon rotates around the earth with the lunar day approximately 50 minutes longer than then the mean solar day. When the sun and the moon are both pulling in the same direction higher tides, known as spring tides occur. Really high spring tides are known as king tides.
Gradually the moon and the sun will fall out of step until their pulls are opposing resulting in neap tides.
The size of tides is not only affected by the direction of the gravitational pulls from the moon and the sun, but also their distance from the earth that changes because their orbits are elliptical. The astronomical phenomena while complex are predictable forming cycles that repeat with characteristics unique to each place on earth, tending to vary in predictable ways with topography and sea depth.
Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.