Tide Patterns

Why are Maui's high tides so weak during winter days?  When are the highest tides?  Are new moon high tides stronger than full moon tides?  Is the Moon always overhead at high tide?  Does the Moon really lift up the ocean to create the tidal bulge?  How are the tides predicted?  If you've always been curious about the tides, you've come to the right place: Maui's Weak High Tides in Winter Anatomy of a Hole Harmonic Tide Analysis King Tides, New Moons vs Full Moons Does the Moon Lift the Ocean to Create the Tidal Bulge? Tide Lagging and Priming Halifax, Long Island, San Francisco References, Acknowledgements, Contact Info

 Here is a plot of NOAA high tide predictions for Kahului Harbor, Maui, in 2023: Watersport folks know that the shallow reefs in Kanaha Beach Park become problematic during winter, and this plot shows clearly how different winter is from summer in Maui in the mid-day. Terminology: " Diurnal" means a once daily tide.  Semi-diurnal means twice per day.   One might think that a word that begins "di-" would mean twice per day, since the Greek root prefix "di-" implies twice.  However, the etymology for diurnal is Latin, from dies (day), diurnus (daily). Many US ports have mainly semi-diurnal tides.  That means there will usually be two unequal high tides and two low tides.  The highest high tide is known as the "high high water (HHW)", and the lower high tide is the "low high water (LHW)".  Maui has been classified as "mixed, mainly semi-diurnal."  In 2024 Maui will have 286 days with two high tides.  On semi-diurnal days, there i

 For reference here is the yearly plot of Maui's high tides: Let's take a close look at the run of high tides that begins on March 1, circled above.  The solid orange dots signify below average High High Waters related to upper transits of the Moon.  This run begins a few days before full moon and terminates a few days after.  At the end of the run, we see a green dot followed by a red dot, and then a gap.  The green dot indicates that this high tide has lost its status as HHW -- now it is a low high water, or LHW.  The tide gets weaker, shows a red dot, then disappears.  What is going on?   Let's zoom in and look at these dates up close: Around the full Moon on March 7, the tides are semi-diurnal, two mostly unequal high tides per day.  The upper transit high tide occurring in the morning starts to weaken, and on March 13 shows a red dot as a LHW below the yearly average for all LHW.  Now the high tides become diurnal, once per day, and the single high tide is related to a

 We now have a good understanding, observationally, of what's going on with Maui's  high tide "holes". The holes appear when the tide shifts temporarily from semi-diurnal to diurnal. The morning high tide disappears and then reappears a few days later several hours later in the day, creating a hole in the time plot.   What is the underlying cause?  It seems clear that Maui's high tides are reacting in some way to the changing configuration of the Earth-Moon-Sun system.  Looking at the runs of high tides leading up to the "holes", one can almost feel the presence of a force that diverts and suppresses morning high tides in the first half of the year.  Is there a way to look under the hood?  How Tides are Predicted Most of you have probably seen diagrams of the forces produced by different Earth-Moon-Sun alignments, complete with tidal bulges and force vectors.  Great minds, beginning with Newton, have worked on mathematical descriptions of the forces that