Why is HT at Springs always at lunchtime?

[fluffc]

So, it seems that I am the odd one out.

From observation, I find that tides move on ever so slightly over the years.

Where I used to work, groups would depart landward across the marsh at 4pm on a sunday. Over recent years, we have noticed that every other week the spring tides are becoming more of a problem as the path covered.

Several years ago, there was no problem leaving the ship at this time, but more recently we find that the path is covered at 4pm. It appears as the later timing of the spring tides cause problems. (Typically one a month).

I agree with all the logic that says that springs and neaps will appear at the same time of day, but my observation is different.

 

[LymingtonPugwash]

Can't be! I've never been anywhere near Langstone! /forums/images/graemlins/laugh.gif Cheers! /forums/images/graemlins/smirk.gif

 

[Kawasaki]

Yoh birdseye!
Yep it was a sleepness eve.
Sometimes my "Body Clock" is as mysterious as the Tides!
I understand the differences of times of Tides around Our shores but My twitterings last Am were aimed at Dave's question ref His locality.
Forumite's posting's ref their Local and Area are all relevant.
Earlier to bed Tonight.
Time and Tide and all that! /forums/images/graemlins/grin.gif

 

[DaveParry]

Thanks all - and good to hear from a local (Kawasaki) on the subject.

I have obviously not been very observant over the years - a symptom of sailing in Clyde waters where (with a few exceptions) you don't need to worry about such trifles. Even the Kyles of Bute is just about managable against a spring tide in the wrong direction. Not so 'outside' of course (West Coast of Scotland).

I shall have to brush up on such things when I move down to Conwy!

Try to get to bed a bit earlier tonight Kawasaki!

 

[Kawasaki]

Yeh but it's different up Your end.
See, if Yer stop the Bagpipe players, Neptune can get some Kip and all will become regulated.
Easy come Easy go,
How der know when to puff or blow?
Those crazy Pipes
I love the sound
Must get Old Neptunes head spinning around
Mull of Kintyre,Scotland the Brave
His poor head We must save
The Day put them away
The Tide goes back and forth each Day
We try to calculate
The Ebb and Flow for this Old Mate
Who gaurds our Sea
Whatever state
The Tide comes in The Tide goes out
That is what it's all about
Time the Pipers quit their wailing
I'm sure it's knackering Our sailing!

 

[cnh]

Well, if you want the full Monty:

Tides

Nicholas Hill

 

[peterb]

[ QUOTE ]
The following give you an approximate answer to tide times - so out with your tide tables and see how far out they are!

[/ QUOTE ]

Quite a long way, unless you know how to use them.

The Establishment of a port is the time interval between the moon's transit and the next high water. To use it to get tide times you also need to know the time at which the moon passes exactly over your meridian (or the antipodes), then add on the establishment to get the next high water.

At full or new moon the Sun, the Moon and the Earth is in a straight line, Sun and Moon on the same side of the Earth at new moon and on opposite sides at full moon. So at new or full moon the lunar transit will happen at the same time as the solar transit; lunar 'noon' is at the same time as either solar noon or solar midnight.

Spring tides usually happen one or two days after the full or new moon. Since the tides lag by about 54 minutes each day, lunar 'noon' at springs will be roughly solar noon plus 3/2 times 54 minutes, i.e. about 1320. Similarly, lunar 'midnight' will be about 0120 (both times local time). Add on to this the 'Establishment' and you will get the time of HW Springs.

So taking Dover, with an establishment of 11h 24m, you would expect a HWS time of about 0048 or 1248. My almanac gives 0027 and 1241.

Similarly, Plymouth has an establishment of 5h 26m. That gives HWS times of 0646 and 1846. My almanac gives 0636 and 1856. Close enough for most practical purposes.

If you're really interested, get a copy of Chart 5058. That shows the co-tidal curves (the curves along which all points have the same establishment) for UK and adjacent waters, together with the co-range curves (the curves along which all points have the same tidal range). Very instructive.