Tides Question?

Dougal

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If anyone here as a little time to spare, please help me out....
Can you please look up morning H/W tide times for St Nazaire (France) on 21st & 22nd Sept 2015

Either I'm doing something very wrong, or something bizarre happens over that 24hr period.

Or of course, I could just be having a VERY long 'senior moment' ;-)

Thanks
 

Dougal

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ProDave

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Look at the SHAPE of the tide graph. The actual highest point occurs earlier or later due to the shape of the graph.

If instead you computed the high tide time as half way between the adjacent low tides, all would appear normal.

(wasn't this same question answered just a few days ago?)
 

Dougal

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I'll search to see. It seemed such an obscure question, I never thought for a minute it might be here.
Look at the SHAPE of the tide graph. The actual highest point occurs earlier or later due to the shape of the graph.

If instead you computed the high tide time as half way between the adjacent low tides, all would appear normal.

(wasn't this same question answered just a few days ago?)
 

Dougal

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dedwards

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Looking at the graph, it looks like HW neaps at St Nazaire lasts for over an hour and on the 21st the highest point of the HW stand is at the beginning of HW whilst its at the end of HW on the 22nd.

In other words, the midpoints of HW @ St Nazaire are still 12.5ish hours apart but the absolute highest times are further apart due to minor differences in the shapes of the curves.

I'm no expert on French ports but I've seen the effect on a number of uk ports. The advice from UKHO is to always look at the curve because sometimes a height difference of a few cm's can drastically change the time of the highest water.
 
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