Well I’m on vacation and away from my copy of Chapmans. But thanks to @rgranger for the link that I can read without toting around dead trees wherever I go.Why don't you just read CHAPMANS or DUTTONS???
In case you aren't aware of them they are called "books."
rg,Here is a good explanation that I have found... (but not in a book - sorry @Stu Jackson
Maybe this is more to your liking - Types and Causes of Tidal Cycles - Tides and Water Levels: NOAA's National Ocean Service Education
David, thank you. That was well written, succinct and answered the question without getting into the whys & wherefores which were but a click away.
oceanservice.noaa.gov
When sailing on Michigan, while not exactly tides, there sure seemed to be something similar....
Maybe you were here during a seiche.
Hi Stu,
Well, I did not read the article, but the exact times between full heights (max high, max low) do not necessarily match the celestial timeline everywhere on the globe. The earth-moon orbital axis creates tidal bulges on opposite sides of the globe. The bulges track the moon in its orbit around the earth. If high tide in Long Beach occurs at noon today, that same high tide should occur at or near 12:50 pm the next day. That’s b/c by the time Long Beach aligns with that bulge on the second day it has “moved” corresponding to the moon’s progress in its orbit around the earth. (In the meantime, Long Beach would have passed under the opposite bulge about 12 h 25 min later, etc.) Consequently, the earth has to rotate for 50 min longer to catch up to the same tidal bulge on a following day. That’s the celestial timeline in its purest sense; so everywhere in the world should experience semi-diurnal tides. But as noted above, not so. Landmasses have an effect. Unless there is a microchip in your tide clock that can be programmed to compensate for variances across the globe the clock will likely eventually deviate from the celestial timeline. For example, it may read half-tide when it’s actually two hr past low tide.
From wikipedia:Well, I did not read the article, but the exact times between full heights (max high, max low) do not necessarily match the celestial timeline everywhere on the globe. The earth-moon orbital axis creates tidal bulges on opposite sides of the globe. The bulges track the moon in its orbit around the earth. If high tide in Long Beach occurs at noon today, that same high tide should occur at or near 12:50 pm the next day. That’s b/c by the time Long Beach aligns with that bulge on the second day it has “moved” corresponding to the moon’s progress in its orbit around the earth. (In the meantime, Long Beach would have passed under the opposite bulge about 12 h 25 min later, etc.) Consequently, the earth has to rotate for 50 min longer to catch up to the same tidal bulge on a following day. That’s the celestial timeline in its purest sense; so everywhere in the world should experience semi-diurnal tides. But as noted above, not so. Landmasses have an effect. Unless there is a microchip in your tide clock that can be programmed to compensate for variances across the globe the clock will likely eventually deviate from the celestial timeline. For example, it may read half-tide when it’s actually two hr past low tide.
Well, that’s what I said. But I suspect your Wikipedia explanation is referring to site specificity. If you set your analog tide clock in Boston and then travel to Halifax, it will be off by the time you arrive. Locations at different longitudes may arrive under the tidal bulge at different times. You need a tide book aboard giving time corrections for different locations to adjust your clock as you travel. Don’t leave home w/o one!
BTW. Just an FYI. Relative to the coastline, tides ebb and flood. Tidal “flow” occurs when ebbing and flooding.
