Tidal Current Tables
Tidal Current Tables are tables that give daily predictions of the times
and speeds of the tidal currents. The tables are issued annually in two
volumes: one for the Atlantic Coast of North America and the other for
the Pacific Coast of North America. These tables are set up basically
the same as the Tide Tables. The Tidal Current Tables consist of five
tables plus a number of current diagrams and data concerning
wind-driven currents, the gulf stream, the combination of currents, and
current diagrams. A brief discussion of the five tables is given below.
Table 1 - Daily Current Predictions. This table gives the predicted
times of slack water and the predicted times and speeds of maximum
current, both flood and ebb, for each day of the year at a number of
reference stations. Also listed at the top of each page is the direction of
set toward which the currents flow. Like the Tide Tables, data in this
book are listed in standard time, so you must add 1 hour to convert the
times to daylight savings time.
Table 2 - Current Differences and Other Constants and Rotary
Currents. This table lists data for subordinate stations. When this data
is applied to the predicted times and speeds at the appropriate reference
stations, reasonable approximations of the current at the subordinate
station may be computed. Later in this assignment, we will use tables 1
and 2 to calculate the speed of current at a subordinate station.
Table 3 - Speed of Current at Any Time. This table allows you to
calculate the current at any time, not just the time of slack and
maximum current. We will work an example problem later in this
Table 4 - Duration of Slack. This table provides a means of
calculating the approximate period of time during which weak currents
not exceeding 0.1 to 0.5 knots will be encountered. This duration
includes the last of the flood or ebb and the beginning of the following
ebb or flood, or half the duration will be before and half after the time
of slack water. Buoy tender sailors may find this table helpful if an aid
to navigation can only be worked safely at slack water.
Table 5 - This table lists data for a number of offshore stations for the
direction and average speed of the rotary tidal current for each hour of
the tidal cycle.