Am I the last to know?

[Twister_Ken]

Looking at this year's Pompey tide tables, it slowly sank in that all the smallest neap HWs are always early morning or early evening, never near midnight or midday. There are 25 smallest HWs this year. 13 of them are within or very close to the 0500-0700 time slot, with the rest in or adjacent to the 1700-1900 window. Conversely, the biggest tides are always close to midnight or noon.

Does everyone else know this? Is it just me? Why wasn't I in the queue when the extra brain cells were being handed out?





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[BrendanS]

Re: Very sad I know

but do you have the Belfield tidal software.
Pick a port, then scroll through the tidal curve day by day ,or just look at monthly HW/LW, it's illuminating when all laid out in front of you

They pretty much all conform to a pattern, that's why they can be predicted?

Had a similar 'road to Damascus' recently when looking at the boattest site, and looking at charts of economy/performance for specific boats. I'll bet most motor boaters don't realise that their peak performance is over such as small speed range

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[peterb]

Yes, but not everywhere. Spring tides at any given port always happen at the same time, but the times are different at different ports. Plymouth, for instance, has High Water Springs at about 7 GMT (am or pm).

It's worth knowing the HWS time for your own port. Then a look at the moon can give you a reasonable estimate of the HW time on any day, just by working out roughly how many days have passed since it was full or new.

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[Twister_Ken]

Allergic to PCs

>do you have the Belfield tidal software<

No, but I do have 4 Apple Macs (and an old one under the stairs)

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[BrendanS]

Re: Fred Drift

but Apple should have beaten Microsoft. Easier to use, more stable, had true 'plug and play' way before MS even got hold of the concept of 'plug and pray'. I took my PowerBook all over the world without a single problem for years. More than I can say for any MS machine I've owned. The deciding factor was the number of applications/utilities/freeware/shareware available to pc owners <s>

Superior technology, OS and software beaten by the overwhelming marketing force and market penetration of MS

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[Mirelle]

You don\'t need a PC a grandfather clock will do...

Long case clocks which show "Time of High Water At ......" are not that uncommon. They were made from the 1680's up to the 1830's.

Of course, the clock only shows the time of HW at the port it was made for.

Long before Tide Tables were published, pilot books showed "The Establishment of the Port" for each port, and this did not mean the Harbourmaster, Mayor and Corporation, but the Time of High Water Full and Change (the time of HW at Full Moon and New Moon) at that place. Early editions of Jack Coote's East Coast Rivers gave it, certainly as late as the 1980's. The assumption is that you will know or can find out the phase of the moon, and work the rest out from there.



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[BrendanS]

Re: You don\'t need a PC a grandfather clock will do...

Some MoBo's still use such things

http://www.ybw.com/cgi-bin/forums/showflat.pl?Cat=&Board=pbo&Number=332157&page=&view=&sb=&o=&vc=1

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[snowleopard]

there is a reason!

high water occurs when the moon is overhead (gravity). spring tides occur when the sun and moon are in line.

therefore: when the high tide is at noon, the sun is also overhead (springs) whereas when the tide is at 6am or 6pm the sun and moon are at right angles (neaps).

and for the pedants...
of course it's never that simple, high water also occurs when the moon is directly 'below' our position and springs also occur when the sun and moon are diametrically opposite. also, because, particularly around britain, tides cause water to slosh backwards and forwards the tides may be advanced and delayed from the moon-overhead time.

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[Little_Russel]

Re: Allergic to PCs

Good to hear that you are an Apple fan, Ken. I have three in the house at the moment.

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[Gunfleet]

Things to know according to PBO

Ken,
There's a great one in this month's PBO where there's a table accompanying Colin Jones's article on tides which solemnly sets out the differences pressure makes to the tides. It starts at 1013 as normal and goes either way. However, since the scale measures the pressure of air over water guess what? 1003 means water will be 10 cm out, 993 means 20 cm, 983 = 30cm (or one foot)... you get it? Amazing!

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[bigmart]

I am sorry but I was told this when I did Day Skipper Classes 20 or more years ago. Tide @ Midday/Midnight Springs. Tide @ 6 AM/6PM Neaps.

Martin

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[Metabarca]

Re: Allergic to PCs

Let's hear it for Apple! I had a classic plugged in for 4 years acting as a mailserver. Never a prob. Now got two at home and an old one in the loft. Still works, still runs almost all my present software; just not a lot of memory.

What's this to do with tides? Er, not a lot, but I can't contribute much to this post as I don't have a tide here (N. Adriatic), or not one worth writing home about.

<hr width=100% size=1><A target="_blank" HREF=http://www.comoy.com/saillinks.html>http://www.comoy.com/saillinks.html</A><P ID="edit"><FONT SIZE=-1>Edited by Metabarca on 20/05/2003 08:15 (server time).</FONT></P>

 

[vyv_cox]

Correct for Dover/Liverpool but not necessarily anywhere else.

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[oldharry]

The you werent taught right I am afraid!. While it is true in the Solent that Springs occur around 12am and pm, on the West Coast of Wales for example, the highest Springs occur around 9 am/pm. But then the tide times there are nearly 6 hours adrift on the Dover tides

Now thats something I never did understand properly - and suppose it is to do with the time it takes the tide to make its way from the western approaches up to Dover. Which means that it is actually Dover that is running several hours behind the Moon...

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[Twister_Ken]

For Solenteers

OK, for those who use Pompey as reference, the AVERAGE time of HW springs (the highest individual tide in each spring/neap cycle) is 12:12 and 00:11. However, there is variation either side of this average. On the noon tides all tides are within plus/minus 1 hour of 12:12, except one at 13:14 and one at 13:26.

On the midnight tide all tides are within plus/minus 1 hour of 00:11 except one at 01:12 (one minute late). Actually for midnight tides all but 5 are within plus/minus 30 mins of 00:11.

I haven't done the same accurate calculation for smallest HW neaps, but it looks like the average morning neap will be about 06:30, the average evening neap about 18:30.

All times GMT, of course.

Biggest springs and smallest neaps seem to occur 2 days after they might be expected from moon phases.

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[bigmart]

Sorry that was a rushed post. I was taught that that referred to HW Dover/ Portsmouth ish.

Martin

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[graham]

Springs and Neaps allways occur at roughly the same times of day in a given port.Eg in Cardiff Spring HW is around 0800 ,neap HW early afternoon.



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[bedouin]

Re: there is a reason!

LOL

That win's the prize for the most inventive spurious argument I've read for years. Actually it reminds me of a comment by a shorebased YM instructor posted here a few months ago - claiming that HW Springs is always near noon.

Just in case anyone doesn't realise that Snowleopard is joking I should point out that that is not the case. For any given port HW Springs is at the same time each month. But a quick check will show that HW Portland (for example) is 4 hrs before HW Solent!




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[Twister_Ken]

Sloshing about

Bedders,

I rather think that is exactly the point that Snowy was making "for pedants" with his highly scientific remark concerning water sloshing about.

Looking at a passage about tides in an Atlantic pilot, it makes the point that away from the influence of land, HW times is that of the meridian passage of the moon. Unlike the Sun, of course, the meridian passage of the moon is not at local noon, but changes by approximately 50 minutes per day, to give the 27-and-a-bit day lunar month.

(And to think this stuff bored me stiff when I was the whining school-boy, with his satchel, and shining morning face, creeping like snail, unwillingly to school. )

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[maris]

Are the highest springs each year, on say a tuesday or do they fall on a diferent day each year????

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