2008 REED’s East Coast Edition - Tides
Tide Table Introduction
The first section contains tide prediction significantly less than the difference between
tables for 57 reference stations. The tables are the tidal day‘s other high and low, or during
organized in geographical order beginning part of the tidal month there is only one high
with stations in Nova Scotia, Canada, and and low per tidal day. In the Gulf of Mexico,
proceeding south along the Atlantic coast there are a several locations that are diurnal,
through Florida, and then north and west with only one high and low per tidal day.
along the Gulf of Mexico, and ending with Illustrated on the opposite page are the tide
stations in Bermuda and the Bahamas. curves for representative ports along the U.S.
The second section, the tide differences Atlantic coast. Note how these curves corre-
table, contains time and height differences for late with the synopsis above. Further note that
other locations (often called subordinate sta- at places with mixed or diurnal tides, it is par-
tions). Instructions on the use of the tide dif- ticularly important to calculate the height as
ferences table (often called Table 2) are found well as the time of the tides. In such locations,
on page 517. the tide cycle is closely related to the declina-
All these tables are based on data collected tion of the moon and its distance from earth.
and maintained by the U.S. National Ocean Information about the moon‘s declination and
Service NOS. The tables are presented in a distance can be found in the monthly pages
custom format using software developed by of a nautical ephemeris, or online at: aa.usno.
Nobeltec. These tables are compact, use times navy.mil
corrected for Daylight Saving, and include Datum: Tidal datums are very much like
sunrise and sunset times for the middle and chart datums; they define the height of water
end of each month. that the chart or table maker has chosen as
Caution: Tide heights are subject to weath- “0.” There are a remarkable number of datum
er influences that cannot be predicted in the names and definitions in use throughout the
long term. world. Theoretically, the tide datum should
Heights: High water is the maximum height not concern the mariner, as it should be
reached by each rising tide, and low water is matched with the chart datum in use for that
the minimum height reached by each fall- location. For instance, if you are using a tide
ing tide. High and low waters can be selected table marked U.S. Datum, 0 ft represents
from the predictions by the comparison of Mean Lower Low Water (MLLW)—the aver-
consecutive heights. Because of diurnal in- age of the lower of the two low waters of each
equality at certain places however, there may day. NOAA charts use the same datum. There-
be a difference of only a few tenths of a foot fore, you may simply apply the tide heights in
between one high water and low water on a the table to the charted depths; at the time of a
given day, but a marked difference in height 6-foot tide over a charted 8-foot bottom, there
between the other high water and low water should be 14 ft of water.
on that day. Therefore, in using the tide tables, Canada uses Lowest Normal Tides (LNT)
it is essential to note carefully the heights as for its charts, which is a significantly dif-
well as the times of the tides. ferent datum than the U.S. LNT is usually
Time: The kind of time used for the predic- synonymous with Lower Low Water, Large
tions at each reference station is indicated by Tides (LLWLT)—the average of the lowest
its name and the time meridian at the top of low waters, one from each year of 19 years of
each page. The tables have been adjusted for predictions (the tide epoch). You may apply
Daylight Saving Time, so no additional calcu- Reed’s Canadian tide predictions directly to
lations are necessary during that period. Canadian charts, but not to NOAA or NIMA
Typical tide curves: All three tide curve charts. With the large tide ranges in Nova
types occur on the East Coast. In most loca- Scotia and New Brunswick, there are signifi-
tions, the tides follow a classic semidiurnal cant differences between LNT and MLLW.
curve, where there are two tides a day of Consult the datum table on your chart to
similar height. In some southeastern waters, calculate the value you should subtract from
the tidal curve tends to be mixed—where the Canadian height predictions to adjust them to
height difference between one high and low is your chart datum.
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