Tidal data diffrences

[MCL]

As complex as tidal predictions are, I am hoping this question is quite straight forward.

I have looked at 3 sources of tidal data today for Tabs Head at the wash.

visitmyharbour time tables says HW 1831 (7.89m) -after BST correction

tidetimes.org.uk says HW is at 1905 (7.5m)

Navinoics android app says HW at 1917 (7.36m)


Why is there so much variation, what do you use and trust?

 

[FWB]

Tucabo Tides Planner app gives 1910 and 7.5m

 

[pmagowan]

As complex as tidal predictions are, I am hoping this question is quite straight forward.

I have looked at 3 sources of tidal data today for Tabs Head at the wash.

visitmyharbour time tables says HW 1831 (7.89m) -after BST correction

tidetimes.org.uk says HW is at 1905 (7.5m)

Navinoics android app says HW at 1917 (7.36m)


Why is there so much variation, what do you use and trust?

I use my keel. It hits the bottom when my depth gauge reads 1m. It never fails.

 

[CFarr]

Because they are estimated predictions that cannot be precisely calculated.
The difference in height on your example is only about 500mm and the mean time is about 1900 so I would go for that and give myself a good safety margin.

I used to worry about these differences until I saw a graph of actual tide heights against predicted ones - they never coincided - sooner, later, sometimes higher, sometimes lower but they were close.

 

[guernseyman]

Tidal predictions for deep sea generally agree to within 2-3 cm. Problems arise in coastal areas and up particularly up rivers - as is the case for Tabs Head apparently. Quite apart from that, such locations are more susceptible to variation from meteorological effects, so clearly your own estimates need a correspondingly large margin for error.

 

[[70521]]

Tide calculations are a mathematical model, different models give different answers. I round everything to the 15 mins and to the nearest 0.50 meter it usually works for me.

Don't foget to consider air pressure and wind, and in our case, river flow.

 

[l'escargot]

As complex as tidal predictions are, I am hoping this question is quite straight forward.

I have looked at 3 sources of tidal data today for Tabs Head at the wash.

visitmyharbour time tables says HW 1831 (7.89m) -after BST correction

tidetimes.org.uk says HW is at 1905 (7.5m)

Navinoics android app says HW at 1917 (7.36m)


Why is there so much variation, what do you use and trust?

There is no such thing as a trustworthy tidal calculation/prediction. Too many variables on the day. Just accept that it is going to (probably) be within an hour and within a foot.