Tidal Coefficients.

Looks good Keith. You're completely right, the French mags very rarely mention tidal height, only the coefficient. We do keep an eye on this for low water fishing - I'll explain next time I see you in case it helps.

A couple of things sprung to mind. The times are UTC+1 which is important if anyone is going to keep this site for future reference.

Also seeing St Helier mentioned reminds me that not everyone realises that LW and HW around the Island might be at slightly different times to St Helier.

I know a matter of 15 minutes might not sound important but in areas where bass are resting up over low water (when we can get the strongest tidal flows in some spots) missing half of the 30 minute window after the tide turns when they go back onto the feed could mean missing half of the prime time.

Not sure how this works/if this applies in the UK though.

Cheers

Paul

I found this on the Wiley Nautical site that may help...

TIDAL COEFFICIENTS



We Brits (well some of us) use Range, the difference in metres between the heights of successive HWs and LWs, to measure the size of a tide. This in turn allows us to call a tide a big one or a small one, or to say that it is a Spring or Neap tide respectively – important information.


In order to arrive at this simple situation you have to look up the heights of HW and LW at the Port and on the day in question and this takes a little time. Such figures will be different whether you are in Oban or off Shoreham, so do not readily stick in the brain cell. There is a better way, much better, for which we have to thank the French (along with good wine, food and cheese). That is Coefficients ...



A Coefficient, whatever the application, is simply a non-dimensional way of expressing size. Non-dimensional means that it doesn’t matter whether we are measuring in feet, metres, lbs avoirdupois or in peanuts or bananas. So the people at SHOM, the French Hydrographic office in Brest, produce a table of tidal coefficients for the year, every day, morning and afternoon.



You, the hard-pressed Vasco, have to remember only 3 figures: 95, 70 and 45. Tack on 120 and 20 to cover the extremes and we can produce a small but meaningful table, comme ça:



120 = a very big Spring tide
95 = a Spring tide (vive eau)
70 = an average tide
45 = a Neap tide (morte eau)
20 = a very small Neap tide



These coefficients are valid whether you are in Leith, Dunkerque or Tilbury. If you doubt that, then think BIG: think Earth, Moon and Sun and little old Europe. Astronomical distances are so great that it is easy to accept that the whole of Europe is subject to the same lunar and solar influences at any one time.


In practical terms, just look up and record in your logbook the day’s coefficient, eg 43/42, just below Neaps – and plan accordingly. In France the times of access to a tidally limited port are often expressed in Coefficients, eg at Binic:
Coefficient 40-50, Access HW –1 to HW; 50-60, HW –1½ to +1¼ ... and so on.


In the Wiley Almanac we colour Spring dates in red, conventionally big and positive; and Neaps in blue, small and negative. Once you’ve got used to Coefficients (allow 5 minutes), you’ll never look back.

Hope this helps...

As I've said, I have researched this somewhat but, still haven't grasped the whole concept.

What I do like is the fact that it removes metric/imperial data from the equation.

Believe me, I would classify myself as fairly clued up re local tidal flows etc..

Yet, If I forget the tide time exactly, I will use my mobile phone to check.
The data is meters. You know, I do not mind admitting, meters mean nothing to me
reference tides. I just cannot visualise meters in fishing. I even struggle with rod length.

And, I've done it for years and years. 11, 14, 16 meter pole fishing, no problem.
I'ver set my float at 7ft though, not in meters or cm. Who can honestly say....

I had a 1.25kg Bass or, my rod is 2.40 ? You'll use pounds and feet/inches

Why we have this issue is beyond me as I'm fairly good at absorbing new stuff.

The same with tide coefficients. It makes sense, sort of. I really want to absorb and utilise
this info in my fishing without making it more complex. Information is power and I feel
we might be missing something here.

Do you know what confuses me? I am like Keith when he says he just dont get meters, I just cant get my head around them. And I also dont do low water sizes either, I tend to say its a 30ft low today. I know what I mean, thats a small nip. And I tend to be able to tell people what kind of height and time the tide is by being able to work it out from the last time I knew for sure, which can be a week earlier or more. So what I am saying is I am confused enough already but get away with it beautifly. I have no idea at this very moment what our tides or time are, but as a guess, total gues, I noticed it was a full moon a couple of nights ago, therefore I would say its a big tide and high about 9 oclock this evening, maybe later,mmm, stab in the dark, todays tide and time is a 34ft and it was high at 10 oclock this evening. I will go and look now. Oh by the way sorry for going off topic.

EDIT: OMG, just checked, its a 35.8ft tide and it was high this evening at 9.18, ah who need these french crazy tide explanations when you have spidey senses eh.

yes.

I have also noted that some big tides don't always come with lowest lows. Loads
of tidal variables that in detail, are hard to process quickly or on the fly.
Like has been mentioned atmospheric pressure makes a big difference, especially here
on our shallow, fast current SE.

Coefficient data sounds really simple and yet, it tells you quite alot.

I'd like to know what the tides where when Nathan and Rob had their best fishing of late too.

If there is one thing in fishing in the sea that influences fish the most, it must be tide and
associated current.

Sometimes, looking at the same data but in a new way can bring a clearer picture.

One thing that I think it does add to our standard way of looking at it in 'heights' is that it makes it very, very easy to find the average tides at your location.

As well as the coefficient, it appears that the French always have the heights as well. To be honest, if I looked at a standard UK tide chart it would be difficult to work out what height the exact average spring or neap tide is, I could estimate but never be sure. Whereas with the coefficient you can immediately tell what the average is as it will coincide with a coefficient of 90 or 45. Why do you need to know the 'average' spring or neap tide height? Well.... you don't necessarily, but it's a useful marker by which to judge everything else. In our own tide charts, I don't belive we have a marker, or a standard set point by which to make comparisons?! Also, tides obviously vary in height around the UK. It may not be so useful on home soil but if you were to travel to another area, knowing the coefficient for that day (which will be the same all over Europe) you can judge in just the same way as you could at home whether the tide for that day was bigger or smaller than the average for that location - without knowing the area.

So, I think its basically most useful when it comes to comparing a tide in one location with that of another - without involving height!

i.e. the tides on the CI's are bigger than ours, but no matter of the distance between areas (over Europe) and how 'high' the tide is, we have a good comparison of when fish are feeding and being caught - without including the actual tide 'height' - which becomes irrelevant and is specific only to area.

In fact, I'm fairly sure I'll start using the tidal coefficient when building graphs and statistics of catches on my site.