smart guys out there, what do the measurements indicate next to the high and low tides?
For example, today in NJ low was .28ft and high was 3.9 feet. I realize that the differential is significant and it impacts surf differently in the area but what are the measurements related to? 3.9ft above what?
Exactly!!! Though, I thought it was above/below sea level. It also depends on the moon's proximity to the earth since our tides are the only visual signs of the moon's gravitational pull. Because our tides depend on the moons location and orbit path, we get "spring" and "neap" tides. Someone correct me if I'm wrong..... but, I believe the spring tides are higher than the neap tides because the moon is closer. So, we had really high tides this spring with some nice storms that ended up washing out some sand to make steep drops off the beach w/ some pronounced sandbars (to tie it into the thread on the OC sandbars).
so how is the 'mean' tide calculated? where do those measurements come from?
Anytime you get completely slammed by a shorebreak closeout- that's one ''mean'' tide.
Sorry, but I couldn't help myself. ''Mean'' tide is essentially an average point, the variance is a combination of several elements including apogee and perogee of the moon in relationship to the earth. Ever consider what the world would be like without the tides? Worse still, without the weather which keeps everything moving from winds to currents to the combination of forces that create the waves. It all boils down to science, and centuries of documentation of earth's many patterns.
Spring tides occur twice a month with new and full moons because the sun and moon's gravitational pull is aligned, the range between high and low is at greatest distance, hence the tide "springs" from high to low or low to high because more water has to move in and out in the same 6 hr timeframe. Neap tides occur with first and last quarter moon phases and the range between high and low is at its smallest because the sun and moons gravity is cancelling each other out (not all the way there is is still a tide). When the moon is at apogee (farthest distance from earth) it has less of a gravitational influence so the tide ranges will be smaller no matter what the moon phase is compared to when it's at perigee (closest distance from earth). Tide times can also be figured by the moon phase, for our area new and full moon= high tide in mornings and evenings (summertime daylight) and quarter moon=high tide at mid day.