Question on Lubec Narrows current prediciton

[EEL]

According to info presented here and that found in a cruising guide, the Lubec narrows current is predicted to be at slack 2 hours before St. John HW and 4 hours after HW.

St. John tides are based on Atlantic time which adds a potential source of error.  I have noticed the Eastport/Lubec HW times are almost identical to the St. John tides in that if HW at St. John is 1300 AST, then Eastport HW is 1200 EST.  While the HW times are nearly identical, the LW times vary, but the current predictions are based off HW.

So why would it not be easier to deduct two hours from the Eastport tides?  Or have I totally mangled the times?

Ed Lawson

Who is busy planning trips between adding logs to the fire.

 

 

[gyork]

Yes, Ed, you are correct that listed HTs between St John and Lubec/Eastport, are essentially the same. Years ago, Rob and I, after a long day from Cutler, were able to sneak under the bridge exactly 1.5 h before posted HT, though a slow current had already started southerly. Good to keep the ROT as 2h before posted Lubec or Eastport predicted HT.

[EEL]

Or aim for 4 hours after HW and have the flood in your favor if late.

Ed Lawson

[Joseph Berkovitz]

My experience planning the bold coast club trips w Bob the last few years has been that slack in Lubec Narrows is about 1.5 hours earlier than Hw/Lw in Cutler. I use cutler to avoid the ADT time zone Confusion but it is only a little earlier than St John. 

two caveats though:

- high/low water in Lubec is considerably later than slack because of the weird flows feeding the area from 3 directions. One time we came through there at dead slack before ebb and left the boats a bit above the tide line — but the water continued rising for another half an hour, a couple of feet at least, and we almost lost the kayaks (embarrassing!). Actually the ebb current started even though the water level was still rising!

- the timing apparently is a bit unpredictable according to local paddlers, there must be some source of randomness somehow. So they say build in extra conservatism.

 

 

Edited February 2, 2021 by Joseph Berkovitz

[rfolster]

On 1/31/2021 at 10:59 AM, EEL said:

So why would it not be easier to deduct two hours from the Eastport tides?  Or have I totally mangled the times?

I think it comes down to who is creating the tide predictions.  NOAA does not have any predictions for the Narrows, but Canada does, probably because it is part of the greater Canadian waterways of Passamaquoddy & Fundy.  Since St. John is the closest major port, all tide predictions are based on that.  Another indicator of this is to look at the chart depths.  Most NOAA charts are in feet, but the couple of that include Canadian waters have soundings in Meters.  Want to guess where they might be getting the bulk of their chart data from?