Capt'n Jack's Tide and Current Almanac is an amazing reference tool. By locating reference points and their current velocities (in the case of the Sound Sound, the Tacoma Narrows) you can determine currents' speeds, as well as ebb, flood, slack, and direction, at other points throughout the Sound. It also predicts tidal heights, moon phase, sunrise and sunset. By understanding the maximum current flow and slack time, you can obtain an accurate picture of a current's speed through time. To do that, you need to use some simple math and the Rule of Thirds...
Rule of Thirds...
With the Rule of Thirds, you divide the time between slack and
maximum flow or vice versa into thirds. Then at the point nearest maximum flow
(either ebb or flood), multiply the maximum velocity speed by 90% or 0.9. The
other point is 50% or 0.5 time the maximum flow.
So, for example, maximum flood is at noon and has a current speed of 1.0 knots. Slack is at 3PM. Using the Rule of Thirds, you would find that at 1PM the current is 0.9 knots (90% of maximum) and at 2PM the current would be reduced to 0.5 knots (50% of maximum).
Now you have a better
representation of the tidal current speeds for a given areas at more
specific times.
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