Coast Guard Aux: New Moon, Storm Will Mean Exceptionally High Tides

Port Jefferson Coast Guard Auxiliary member gives advice on boats in the water during the storm.

Although much info can be found on general hurricane preparedness, there are some recommendations that I would mention specifically for north shore boaters “in-the-water.”

First, as with any area where strong winds are imminent, it goes without saying that anything that acts like a sail should be taken down. This means that canvases and vinyls should be removed and stowed, allowing the gusts to "blow through." If mooring covers are available, use them so as to make yourself more aerodynamic.

Next, and more important: We have a unique situation in that we experience a bi-daily tide change of typically 6 ft on the average.  Hurricane and tropical storm conditions generally cause unpredictable tidal swelling. In this upcoming storm, it is compounded by the fact that we will have a “new moon.”

When the moon is full or new, the gravitational pull of the moon and sun are combined. At these times, the high tides are very high and the low tides are very low. This is known as a spring high tide. Spring tides are especially strong tides (they do not have anything to do with the season Spring.) They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon.

In preparation, north shore boaters must consider the implication this extreme tide height may have with regard to the way most of our marinas deal with tidal change in general.  The typical slip configuration affixes a boat to a floating dock at one end and at the other end the boat is tethered to a ring that slides on a pole attached to a piling.

Most boaters agree that “crisscrossing” the stern lines (attached to the dock) is prudent since the dock and boat will follow any tidal changes together. The problem lies in the bow and spring attachments, since the piling doesn’t move. If the tide surges beyond the limits of the attached slide pole, either the pole breaks or the cleats get ripped out of the boat, either situation leaving the vessel dangling free at one end.

So, there is no one solution appropriate for every boat, situation, or slip; but instead the recommendation is to analyze your dock space and imagine your boat, say, ten feet higher than where it is now.  Then adjust the slack in your bow and spring lines to accommodate that extreme, and supplement the lack of “tautness” in your lines with additional fenders (placed horizontally or vertically with fender-boards) to protect yourself from banging against the pilings. Supplementing, also, with firm stern cross-tying and fendering to the dock.

In the most extreme case (Cat 4 or 5), if you were unable to get your vessel out of the water, then we would completely abandon tethering to the pilings and tie all the boats in a marina together.  This way they would all move in unison; like a big blanket.  That, of course, would require a huge communal effort, with discussions and debate that would last until the next big storm. But let’s hope it never comes to that!

Just my $0.02.

Carl P. Palmblad
Past Flotilla Commander
USCG Auxiliary-Port Jefferson, NY


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