What is the lunitidal interval?

The lunitidal interval is the delay between the passage of the Moon and its effect on local tides. In principle, local high tide should occur when the Moon is precisely at its apex overhead, but the effect can be delayed by the topography of the coast and sea floor.

Calculating the local lunitidal interval requires an awareness of such conditions as the shape of the coastline, the slope of the continental shelf and a number of other factors that affect the movement of ocean water. In places where the topography is complex, such as New York harbor, the interval can be as high as eight hours.