cape cod tides... thanks!
Thanks Adrian and Juro for the links!
Kush probably provided the key to why the bi-weekly tides usually repeat: when you revisit the same site two weeks later you are visiting at the OTHER tide, for example if you were on the high high tide two weeks later you will be on the low high tide. If there is a slight time difference between these tides it will add on one bi-weekly tide and subtract on the next bi-weekly tide. Apparently this is what creates the common pattern of match then jump in bi-weekly tide times on the Cape (there are periods where this does not happen due to all of those other complications). (so Kush can even teach old dogs...).
I have a copy of Eldridge and "The Fisherman's Ocean" but some of these things are obviously useful only if you have a good sized boat. IF you use a Pungo or canoe your world is quite different. I think I can paddle against most currents in Chase Garden Creek (a small tidal stream draining into Cape Cod Bay), but I doubt that I could make it upstream against the current in Bass River at the railroad bridge when there is a pretty good "lump".
Tomorrow I may get down to the Cape but with the very cold temperatures lately may not see familiar water but ice. The last time I was down the ice flows in the Cape Cod Canal covered about 30% of the surface. There may be some "scouts" at the Bourndale herring run but, if so, they will surely be winter crazed fishermen staring at the run, not herring.