Astronomical Spring Tides!

bilbobaggins

bilbobaggins

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Forumeers might like to be forewarned of the astronomical tidal ranges predicted for 1/2 March :

Big tides

Here's what it suggests for the head of the Bristol Channel:
1/Mar/2006 -0.10m 2/Mar/2006 14.47m Range = 14.57m or 47.80 feet , in old money.

All that's needed for M&S shoppers in Guernsey to wear waders, or a dozen flooded marina car parks around the Solent to need tractors, is some low pressure at the same time. And if that's in the North Sea, expect a big storm surge.

Remember, every 10 Hectopascales ( er, millibars for the traditionalist barometer! ) below 1013 equates to another 10 cm. ( 4" ) extra high water......

And there will be far less water at LW, so groundings on bars and shallow channels are likely. Anyone for cricket on the Shambles Bank?
 
That's odd, Mike, my tide tables show the heights for Plymouth (Devonport) being signicantly lower in Sept and Oct than March. What's even curiouser is the difference in heights quoted in the tide tables issued by Weir Quay and others based on Proudman Institute fugures and those in the Plymouth Yacht Haven booklet (source unattributed). The former are higher than the latter throughout.
 
More lunar and solar than astronomical.....

Predictions for LW are certainly lower than Lowest Astronomic Tide, but please take issue on terminology with the Hydrographer of the Navy at Taunton - he's bigger than me!

....and it's probably better than by Astrology! /forums/images/graemlins/laugh.gif
 
"......and you can choose the port you are interested in..... VicS"

Yawn! The devil is in the detail, and most users of this - or any other - forum would be well acquainted with the concept of 'rollover buttons'. The top banner of the site lists, among several other services accessed by rollover buttons, the option 'Tidal predictions'. Drilling down just a little deeper, via 'Highest and lowest tidal predictions' takes one past some other useful options to the page indicated by Mr Vic.

Get a life..... /forums/images/graemlins/wink.gif

More importantly, anyone expect to be inconvenienced on the water by these near-extreme tidal ranges?
 
I find the NTSFL site difficult to navigate! In part that is because once one has followed a link to particular page that link reverts to the same colour as the rest of the text so it is difficult to find again until you run the mouse over it and the underlining shows up. I still can't figure out the purpose of the screenfuls of numbers not apparently related any particular ports that appear by following your original link. I guess I'm just thick.

However one thing which has often puzzled me are the tidal preditictions that go negative. If chart datum is equal to LAT then how come low tide predictions can go below it. Eg for Weymouth on 28 Feb it goes to -0.15m. which the Weymouth page does tell me is LAT so why is that not Chart datum and low tide on that date 0.00m?

Is this because chart datum is only equal to LAT for the limited number of standard ports and that for (secondary) ports like Weymouth tide heights are calculated relatve to the datum at the standard port?

Sorry, looking for a life away from "Strictly come ice skating " and "Emergency Ward 10" "Dr. Kildare" or whatever it's called these days.

[ QUOTE ]
More importantly, anyone expect to be inconvenienced on the water by these near-extreme tidal ranges?

[/ QUOTE ] What will be an inconveniece will be if a neap tide is ever so small that it fails to reach the yard slipway. The tables on the NTSFL site don't show data for neap tides however.
 
My info comes from my RNLI Diary whose tide tables are for Dover and are produced by Proudman Oceanigraphic Laboratory. Their tidal height predictions for HW on the 9th and 10th March are for 7.0m but for 10th September and 9th of March 7.2m!
 
my tide program (Belfield) shows springs tides at Dover are on 2nd March this year. Height 7.62metres. It shows neap tides on the 10th.

Before I start checking out my software are you using the 2006 diary or last years?
 
[ QUOTE ]

1/Mar/2006 -0.10m 2/Mar/2006 14.47m Range = 14.57m or 47.80 feet , in old money


[/ QUOTE ]

thats good, portishead will be on free flow /forums/images/graemlins/wink.gif

Sharpness is the head of the channel, and will be a bit smaller about 10.4 - biggest tide will be newport with about 15.1m
 
We make sure that we are in attendance during any tides over about 5.4m at Salcombe, if our boat is alongside the quay wall.
If there is low pressure and/or strong S'lies the boat can end up sitting on top of it /forums/images/graemlins/blush.gif.
 
Sounds more like 1st April to me.... Chi Harbour tides are predicted at 5.2m which is the highest they normally go in our part of the world. But nothing out of the ordinary - unless we get a vigorous low and strong Souwesterly with it....

Same height prediction for 10/9, and 9/10 on the 'official' CHC tide tables.
 
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