Gulf of Mexico tides

TMHeimer · Feb 13, 2014

Can't find a good sub forum for this, so I'll ask here--mods please move if there is a better place. I am very familiar with the diurnal tides of the Gulf of Mexico (especially the Eastern Gulf). One thing puzzles me. For the 3 months of Jan. Feb. March there are a total of 28 high tides between 11:55 A.M. and 4:47 P.M. (prime daytime dive time). There is one low tide March 1 at 3:26 P.M. (following the 1:19 HIGH tide--that usual "switch over" thing). It was the same last winter-- one low tide. Why are there not more than one low tide in those 3 months during that afternoon timespan?

tursiops · Feb 13, 2014

The eastern GoM is dominated by the diurnal tide....so one high and one low per day.....and you are only seeing the high because you are not looking over the entire 24h period. But there are some other tidal constituents too...like the semi-diurnal, with two highs and two lows per (lunar) day. Usually, all you see is the diurnal...but now and then, like biorhythms, things get in/out-of-sync, and one of the semi-diurnal lows shows up. it might make more sense if you looked at the full 24h period and not just the "diving day. "

TMHeimer · Feb 13, 2014

tursiops, Yes I understand all that (Grew up/live on the E. Coast). Over the 24 hour periods every day (except that one) in that 3 month period, the low tides don't come near that 11-3 daytime period. They are late at night (or in the wee hrs.) on those 28 days when high tide is between 11-3 in the day (of course approx. 12 hours later). The other low tide times centre around 6-9 A.M or 6-9 P.M. So same question--why only one low between 11-3 daytime? --in those 3 months., the last 2 years (and always?).

tursiops · Feb 14, 2014

There are many tidal constituents, each with their own frequency and strength, for each location. How they interplay is the key. In much of the eastern GoM, the main constituent is the diurnal...but it is not the only one. As the positive and negative reinforcing of the various frequencies comes and goes, one of the other constituents may pop up momentarily as relevant. That is what you are seeing.

That is the short answer. For the long answer, see Wiley: Tidal Hydrodynamics - Bruce B. Parker.

TMHeimer · Feb 14, 2014

tursiops, Thanks--I'm a little bit closer to understanding. You're saying one of the other constituents causes this. I should mention that I checked NOAA through June 2014 and there were still no low tides between 11 and 3 during daytime. Can't click on anything nor afford the $369 for the Parker book. A MI and an OWSI here in Destin could not explain it. Can any panhandle local explain why there are basically no low tides during that 11-3 daytime period from Jan. though JUNE (maybe always????--I didn't check NOAA past June--we are only here in winter so I don't really care), yet there are high tides here and there DURING THAT DAYTIME PERIOD? Am looking for a simple layman's answer--maybe there isn't one, or simply no one knows it.

tursiops · Feb 15, 2014

Click through some of these for the weeks where you do and don't get your mid-diving-day low.
Tide Predictions - PANAMA CITY 8729108 Tidal Data Weekly View - NOAA Tides & Currents

You'll see the bumps in the curve that are not quite lows...and then they grow and pop out. This is the interplay of the various constitutents, or tidal harmonics.

I was only kidding (a little) about the Parker book; it is the best resource, but mostly it was written by a friend...always trying to help him sell a few! The NOAA COAPS site is very good; Bruce used to run that operation.

TMHeimer · Feb 15, 2014

Thanks for all the info. I stand corrected in that low tide does occur twice in March during the timespan I rant about. It seems that once you get to Aug. and later in the year the lows occur then more often between 11 & 3 (this is what I figured would be the case in Jan.-March, or anytime). I guess it's not really my lack of knowledge on the matter as to exactly why there are basically no lows at that time that knaws at me. It is that 2 experienced instructors here seem to insist that this situation does not occur! I have told them to just check out the times on NOAA--it's all right there.

Gulf of Mexico tides

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TMHeimer

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tursiops

Marine Scientist and Master Instructor (retired)

TMHeimer

Contributor

tursiops

Marine Scientist and Master Instructor (retired)

TMHeimer

Contributor

tursiops

Marine Scientist and Master Instructor (retired)

TMHeimer

Contributor

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