King Tides, New Moons vs Full Moons

 Here is a plot of every predicted high tide at Kahului Harbor in 2023:





Intuitively, one might imagine that  "new moon tides are more powerful than full moons due to the moon and the sun pulling together from the same side of the Earth."  We will deal with the theory in the next blog post, "Does the Moon Really Lift the Ocean?", but for now let's just look at the data.

New Moons vs Full Moons

From the figure above we can see that for Maui at least, full moons are just as influential, and in fact there are more full moons where the associated high tide is significantly higher than its new moon neighbor tides.   We do see a peak in tide heights in January, which is probably due to the Earth reaching its closest approach to the Sun on about January 3.  

King Tides

But the highest tides appear to be in summer, with the peak at full moon on August 1.  What causes this?  One would think that summer higher tides would be associated with the Sun being highest in the sky in the northern hemisphere and thus exerting more force on the tidal "bulge."  If that were true, why isn't the maximum centered on June 21, the summer solstice, when the Sun reaches its highest point?

Here is a list of the top 20 predicted high tides for 2023 for Kahului Harbor, Maui:


Note the dominance of July and August, whereas December-January accounts for only 5 of the top 20 tides.  

Here is a 5 year plot of HHW heights, showing the relative stability of the summer maxes.  Vertical lines are shown on the half year intervals near the summer maxes:


For completeness, here is a list of the top 20 low tides for 2024:










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