Slack, Flood current, and ebb current

[JohnHuth]

The attached figure is some esoterica I played with for an upcoming trip out of Jonesport, ME.

One of the things we like to do before a trip is make sure we have information about the tides and currents. Since downeast Maine is famous for both of these, I wanted to investigate a bit. Now, we might put all this information down as numbers in a table for reference, but I wanted to look at it graphically just to see what was going on and try to make sense out of it.

First - the period of the graph is June 22 through June 27th. There is a full moon early on in this period - and it has a declination of -20 degrees - reaching its largest right around the time of the full moon. The sun has a declination of +23 degrees, so you're getting a lot of tidal whallop going on in this period. The low tide drops a couple feet below MLLW.

Another thing I wanted to do was correlate current and the phase of the tide itself. One would naively think that slack tide would correspond to the high and low tides, and that the maximum flood current would come halfway between a low and high, and that the maximum ebb would come halfway between a high and a low. You can take a look at the graph and decide for yourself - I point out the time of slack, max flood and max ebb along with the tidal cycle - it's interesting when they occur.

You might also notice a difference in the size of the tide depending on the timing of the moon. A "near transit" is when the moon passes directly overhead - on the "meridian", which is a line that runs from due north, through the zenith and then due south. The "far transit" when the moon is on the other side of the earth from us.

The tide data were from Steele Harbor, the current data from the east end of Moosabec reach - these are close enough to each other to basically be the same (little variation in tide heights)

Edited June 13, 2013 by JohnHuth

[josko]

John, if you send me your email to jcatipovic at hotmail... I'll send you a hopefully intersting animated tide atlas for the area.

[EEL]

It is interesting to compare the the max flood and ebb as well as slack times for the east and west ends of Moosabec Reach. Substantial differences. I think it might be enlightening to know what the times for the current would be at the Steele Harbor Island tide station location as well as the tide levels at the current locations. My limited experience is that in locations with high tide currents you can have rather sudden water level shifts. The points of discussion here are not fast current areas as such, but that whole area has currents which play a big role in paddling plans...or so I believe given my wimp paddler status.

My SWAG is that as kayakers we often are faced with currents that cannot be gleaned from the few current stations since we are paddling in locations with very localized currents and locations of no interest to commercial navigation so there is no listed information.

Ed Lawson

[NateHanson]

That is indeed an interesting area for tidal planning, isn't it? It's unique both in the complexity of the currents/tides, but also in the relative abundance of tidal current prediction stations. What other prime kayaking ground on the maine coast has 3 current stations within about 5 miles of eachother?

That said, my observation is that the East Moosabec Reach current tables are good primarily for that one spot (and presumably also for the west side of Roque Is.). They do not tell you much about the current in Eastern Bay. In Eastern Bay, the current floods nearly until High Tide at Steele Harbor, while the East Reach current station would have you guessing that Eastern Bay starts to Ebb two hours before High Water.

In Western Bay, the West Moosabec reach station is about right for Western Bay in my experience.

Ed, there is unfortunately no tidal height prediction given for the current stations, and no current prediction given for the tidal stations. So direct comparisons are not possible. And you're right - the current in these specific locales are not strong in the "reversing falls and whirlpools" sense, but recognizing the eddies will often make the difference between moving at 4 knots and 3 knots. Also, you'd better time the current if you wish to pass under the bridge, because at higher tidal ranges kayaks can't attain under the bridge at max flow, so in that one spot it's particularly critical. In my experience, the current under the bridge resembles the Western Reach current station, moreso than the Eastern Reach station.

Nate