Doesn't the Isle of Wight have four tides, and where we are at the mouth of the Exe the tides can be different to other places locally due to the restricted inlet opposite Exmouth docks, also when we have a lot of floodwater coming down the river the tides can be different to those publishes in the tide tables, I expect that the Thames is similar, love Hammersmith bridge by the way!
I know less about tides than I realised
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Southampton/Isle of Wight gets a double peak something like this, not two tides but a very useful longer period when harbours etc can be used.
which is due to that resonance thing I referred to . Remember it comes UP not IN, so it's nothing to do with the island being there..
Many things turn out to be resonant- dependant. Movements of planets etc too. Gravity is a spring and everything bounces...
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Double high tides are usually caused by the water flowing out so fast through a restricted outlet that the volume of water rises as it goes through. The strength of the tide is usually caused by the position of the moon relative to the sun. With a Neap tide the pull is weaker so the height of tide is less, with a spring tide the pull is strong and the height is greater. The height of tide pretty much determines the speed of the water and the time the tide is slack.
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I think that would be for an extended high tide - the Channel has double peaks even where there's no restriction. IE it goes down a bit then back up.
@gone said Poole, which sounds right. There are animations out there..... There are other places, which I've forgotten.
As I'm typing I vaguely remember something about the tide peaks in the N Sea being different from those in the Atlantic, which is part of the story.
Can't find any, this alludes...
TIDES:●amphidromic point○A “no-tide” point in an ocean caused by basin resonances, friction, and other factors around which tide crests rotate. About a dozen amphidromicpoints exist in the world ocean. Sometimes it’s called a node.
Same source said tides were on an 1800 year cycle. Eh? Blimey.
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On your diagram for the iow. You have the effect of the southbound tide when it turns. It doesn’t go east then west etc , it swings south for about 40 mins - that tends to back up the medina a bit
See tonight’s
See tonight’s
Dead simple. The sun and moon cause the sea to bulge where they are having an effect.
Then it gets more complicated. The bulge causes flow. In some areas the flow is restricted. In some it isn't. That results in specific high and low tide times around the country. Also different heights.
Then it gets more complicated. The bulge causes flow. In some areas the flow is restricted. In some it isn't. That results in specific high and low tide times around the country. Also different heights.
Imagine viewing the whole of the Uk from a greater height. What you see is an island. When the Atlantic is pulled away from the island, towards the West for example, the overall sea level around the island is lowered. This allows water from tidal rivers and estuaries (including the Thames) to flow into the seas. Some of these rivers and estuaries flow towards the East.
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No, that description is wrong, though I don't know what you're trying to say. Nobody said the water went east then west
No, not dead simple at all, as has been explained.
Look it up.
No not right either, saying it's pulled away is misleading.
The Thames is tidal up to about Kingston/Richmond, and rather obviously, rivers flow towards the sea.
LOOK IT UP, folks.
The tides are (obviously) later towards the east, but the double high tide is a result of oscillations and resonances.
I'm sure you'll all find bits of this to support each oversimplification, but standing alone as presented, they're incorrect.
Southampton Weather - Double Tides
Officially the most up-to-date weather reporting live from Southampton. With the very latest forecasts, charts, weather tv, marine info, astronomy and much more.
More evidence that things aren't as facile as described above - https://www.ntslf.org/tides/tidepred?port=Portsmouth.
Note, the tide range reverses on alternate days, when the range is lower
There are several drivers combining. The gravity effect is like voltage, but there are effects which behave like indictors/capacitors/resistors. You can model a body of water in those terms and get an idea, and see resonances, but there are always non-linear local effects.
It's just another situation where a glib description may be compelling, but it doesn't stand much chance of being right.
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The best questions are those which turn out to have long - in this case never-ending, answers
It makes me smile when for example, if you sit and watch a tide peak, the tables aren't quite right! Same with eclipses etc.
How the heck they used to calculate these things without Matlab, is a bit of a mystery I can live without delving into.
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I wasn't arguing with you, I was offering an explanation as to why there is a backing up of water in the mouth of the Medina.
It gets very anal in the "boatist" world. For yacht master theory for example you are expected to calculate tides for secondary ports where the tide is between Spring and Neap. Here you have to use interpolation to work out the tidal curve based on the difference between the reference port at High water and low water for each of the spring and Neap tides. Its all designed to be done without a calculator.
You end up spending 15 minutes doing a bunch of maths, to calculate a height of tide in a port at a specific time, only to find out that your rough guess was within 10cm. Its all calculated anyway, and often atmospherics make a bigger difference. Nobody in their right mind will say, I will arrive at 3:46PM because the height of tide above chart datum (lowest astronomical tide) is exactly 2.45m and I draw 2.3M, so 15cm is plenty for me not to run aground. Good luck with that plan.
No need to. I have directly made use of tides. Current rates are of less interest to my use of them other than some -places needing more lead on the end than others.
As I said dead simple but then comes the complications.
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