Gloucester, MA Tide Gauge

Funded by NERACOOS. Data is reported in elevation above MLLW (NAVD88) in feet and also converted to meters.

NOAA uses Mean Lower Low Water (MLLW), which is the average height of the lowest tide recorded at a tide station each day during a 19-year recording period, known as the National Tidal Datum Epoch.[5] MLLW is only a mean, so some tidal levels may be negative relative to MLLW; see also mean low water spring. The 19-year recording period is the nearest full year count to the 18.6-year cycle of the lunar node regression, which has an effect on tides.