2008 REED’s East Coast Edition - Currents Tables
Tidal Current Table Introduction
Reed’s tidal current prediction tables cover there is a rotational and/or geographical
primary reference stations located on the east component that causes a less regular current
and gulf coasts of North America. The tables cycle, sometimes even double floods or ebbs.
are organized geographically, beginning with In areas with mixed or diurnal tide curves, the
stations in Nova Scotia, Canada, and proceed- current curve also tends to be irregular.
ing south along the Atlantic coast through The tidal current tables indicate for each day
Florida and then north and west along the of the year the times of all slacks (minimum
Gulf of Mexico. current flow), times of maximum ebbs and
The current differences table (often called floods, and the maximum current speed in
Table 2) provides predictions for additional lo- knots. The approximate direction in degrees
cations, and there are special difference correc- true of the ebb and flood currents is also in-
tions for a number of near-shore and offshore dicated in the top right-hand corner of each
locations that exhibit rotary behavior. Finally, tidal current table.
there are current chartlets for six sounds and As in the tide tables, times in the current
bays between Cape Cod and Cape Henry. tables are local, on a 24-hour clock, and have
All these tables are based on data collected been adjusted for Daylight Saving Time, so no
and maintained by the U.S. National Ocean additional calculations are necessary during
Service (NOS). The tables are presented using that period. There are usually four slacks and
software developed by Nobeltec. four maximums each day. If one is missing on
All tide and tidal current predictions are a given day, it may occur after midnight, as the
approximations and are subject to weather first slack or maximum of the following day. At
influences that cannot be predicted in the some stations where the diurnal inequality is
long term. large, there may be on certain days a continu-
Where tides are semidiurnal, there are usu- ous flood or ebb current with varying speed
ally two ebbs and two floods per day of similar throughout half the day, giving only two slacks
speed. In a few places like Portsmouth, NH, and two maximums on that particular day.
Notices
BOSTON HARBOR, MA: The current at from the sea during flood tide with northeaster-
Deer Island Light has a rotational component. ly winds. A similar but less serious situation oc-
Regard “slack” times as only minimums, and curs when leaving the port during ebb tide. The
flood and ebb directions as only averages. At Coast Guard reports that ships may encounter
times of slack water before maximum ebb, the current anomalies at the mouth of the Miami
speed actually averages 0.3 knot in a direction River that have caused occasional groundings.
of 184°T.” ST. AUGUSTINE, FL— ATLANTIC IN-
WOODS HOLE PASSAGE, MA: In the TRACOASTAL WATERWAY: The USCG has
narrow part of Woods Hole Passage (current reported a problem involving the tidal currents
location: “Woods Hole, 0.1 mile SW of Devils in the Intracoastal Waterway at the Bridge of
Foot Isl.” based on Cape Cod Canal), current Lions. Numerous current-related accidents
speeds may exceed predicted values by 10% have occurred, as boats moving with the cur-
to 20%. Currents up to 5 knots have been rent lose steerage under the bridge. There is no
reported. Woods Hole currents shown on tidal current station at or near the Bridge of
the “Buzzards Bay/Vineyard Sound” current Lions. The Bridge of Lions is a difficult bridge
charts should not be used alone as they do not to navigate, even under ideal conditions. This
account for changes since the 1931 survey. 1926 bascule bridge has a horizontal clearance
BISCAYNE BAY/PORT OF MIAMI: The of only 76’ versus the 90’ horizontal clearance
Biscayne Bay Pilots report variances between of most of the other bridges on this section of
predicted and actual currents. Caution should the AICW. In addition, tidal currents in ex-
be exercised when entering Government Cut cess of 2 knots often run at right angles to the
bridge opening. Use caution.
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