A “tidal day” generally has a duration of 24 hours and 50 minutes, and contains one complete tidal cycle (sinusoidal in shape),with two highs and two lows. This erxplains why successive high tides are about 50 minutes later each day.
Ocean tides have complex spatial patterns, due to the complicated shapes and topographies of the different ocean basins. In general, however, ocean tides at any spot usually consist of a mixture of semidiurnal and diurnal tides. The basic pattern may be distorted by the effects of landmasses, the complicated shapes & topography’s of ocean basins, constrained waterways, friction, the Coriolis effect, or other factors.
There are three basic types of tidal patterns.
l: Most areas have two highs and two lows a day. If the two highs and the lows are each respectively about the same amplitude, and is called a semidiurnal (semi-daily) tide .
: When the highs and the lows each respectively differ in height (where a single
low tide follows two high tides) the pattern is called a mixed tide (Pacific basin).
: Some areas, such as the Gulf of Mexico
, have a diurnal tide with only one high and one low tide each day (and the range is often small).
As the sea level rises and falls, it generates a tidal current
that flows horizontally. Tidal currents caused by the dropping water
level (as the tide "goes out") are called ebb currents. The rising tide generates flood currents. The rule of twelve normally predicts the higher velocities will occur in the middle two, of six hours in a semi-diurnal pattern. With a diurnal pattern, in the Gulf, you would expect the highest velocities in the middle four hours of the 12 hour pattern.
As previously indicated, these are approximations only.
Hope this helps,