Example
Similarly, the time of maximum flood in
Suppose you are interested in tidal currents
the New River can be computed by subtract-
in the New River, Fort Lauderdale, Florida, on
ing the time difference of –0:39 minutes
March 25. This location is listed in the current
shown under the max. flood heading from the
differences table in the Place column, under
times of maximum floods shown in the Mi-
the Florida, Atlantic Coast, subheading, and is
ami table (0647 and 1905). Maximum floods
keyed to the Miami, Florida (Harbor Entrance).
in the New River will occur at 0608 and 1826.
The current differences are calculated for an
The Speed Ratio figures allow you to deter-
approximate position in the New River of 26º
mine current speeds at the current difference
06.73’ north latitude, 80º 07.18’ west longitude.
station at the time of maximum flow for a spe-
Now you would turn to the time and speed
cific day (which may differ from the average
entries in the Miami current table for March
maximum flow speeds presented in the final
25. For the example’s sake, let’s say we find
two columns of the table).
predictions that look like this (This is example
To figure the approximate maximum flood
data, not this year’s data):
speeds in the New River on March 25, multi-
ply the maximum current speed under the Fld
heading for the relevant times in Miami (1.8
for the first flood and 2.0 for the second) by
the speed ratio for the New River given under
the flood heading (0.4) in the current differ-
The current is at maximum ebb (1.6 knots)
ences table:
at 0133; slack at 0431, at maximum flood at
1.8 knots (0.4) = 0.7 knot
0647 (1.8 knots); slack at 1018, at maximum
2.0 knots (0.4) = 0.8 knot
ebb at 1308 (1.6 knots); slack at 1646, at
To compute the approximate maximum
s
maximum flood at 1905 (2.0 knots); and slack
ebb speeds in the New River on the same day,
again at 2246.
multiply the speeds under the ebb heading for
To find the time of slack before ebb in the
Miami (1.6 for both ebbs) by the speed ratio
under the ebb heading (0.3) for the New River:
u
r
r
e
nt
New River, the time difference of –0:06 min-
C
utes under the Slack before ebb heading in the
1.6 knots (0.3) = 0.5 knot
current differences table should be subtracted
Information in the Current Direction and
from the slack times before the ebbs (1018
Max Speed columns is read directly. At the
and 2246) in the Miami table. Minimum cur-
time of maximum flood, the New River cur-
e
s
rents before ebbs will occur at 1012 and 2240
rent flows 005° true; at the time of maximum
ebb, 130° true. The average flood maximum
n
c
in the New River.
speed is 0.8 knots; the average ebb maximum
re
Similarly, the time of maximum ebb in the
New River can be computed by subtracting
speed, 0.5 knots.
i
ffe
the time difference of –0.16 minutes shown
D
under max. ebb in the current differences ta-
n
t
ble from the times of maximum ebb in Miami
(0133 and 1308). Maximum ebbs in the New
u
r
re
River will occur at 0117 and 1252.
C
To find the time of slack before flood in
the New River, the time difference of –0:43
minutes under the slack before flood head-
ing should be subtracted from the slack times
before the floods noted above for Miami
(0431 and 1646). In the New River, minimum
currents before floods will thus occur at 0348
and 1603.
691