EasyTide Portsmouth: double HW?

Looking at the times and the differences between the heights of the 2 HW it is more of a stand. My Absolute UK Tides app which uses the same basic data shows only one time for Wednesday morning HW rather than 2 - and roughly halfway between the 2 Easytide times, but a different height at 4.8m rather than 4.7m.
 
Portsmouth and Hayling are islands, just like the IoW and the tides behave in similar manners. The IoW is much bigger and the openings for Portsmouth, Langstone and Chichester Harbour so small that, unlike Southampton, the difference in Portsmouth and Langstone is normally barely noticeable. Looking at the tidal streams, however, you'll see that water continues to flow into Portsmouth after nominal HW and out after LW.
 
Yes I think you're both right; Portsmouth and the Solent ebb tides is basically HW, then a couple of hours of nothing much then whoosh for three hours. Curiously EasyTide's data seems to be somewhat inconsistent with its own graphs, although nowhere near enough to be of any relevance for nav purposes.
 
RobbieW said:
A very familiar phenomenon to anyone based on the Hamble ;)
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Funny you say that: last year Xxx from Hamble executed a nifty ferry glide into Treguier Marina, sliding serenely down an alleyway and into a berth with the water flowing through the pontoons at about 3.5kts.

The missus commented, "Not bad!" ..."It's Darwinian!" I told her :rolleyes:
 
dom said:
The UKHO's EasyTide website has been showing double HW readings for Portsmouth for a few days now. Any idea as to what's going on?
http://www.ukho.gov.uk/EasyTide/EasyTide/ShowPrediction.aspx?PortID=0065&PredictionLength=7
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Interesting because although it lists the double HW figures in the table the second high does not show up on the graph even when you expand it to show one day at a time.

Try these if it makes life any esier

http://www.ntslf.org/tides/tidepred?port=Portsmouth
 
YM reviewed Tide Apps a couple of month's ago and included the Southampton equivalent of the Liverpool data. However much the same information, but based on the HO data rather than observations is better displayed on the Absolute App that I bought - the App is free but the data is £2 for the year.
 
dom said:
The UKHO's EasyTide website has been showing double HW readings for Portsmouth for a few days now. Any idea as to what's going on?
http://www.ukho.gov.uk/EasyTide/EasyTide/ShowPrediction.aspx?PortID=0065&PredictionLength=7
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As I don't think anyone answered your question directly, but its going to be confusing to many Solent sailors, it's worth noting that UKHO have updated approach to what 'HW' means in this case. Its not the single point of inflexion of the highest point of the tide, but can be the start or end of a HW stand in which there isn't a significant change. They've updated their FAQ and provided a document explaining this change:

The FAQ now states:
"This relates to a change in how the predictions are shown at the more complex ports along the south coast of the UK, in particular the Solent, based on customer feedback. It involves the identification of the start and end periods of High Water ‘Stands’ (i.e. the prolonged period of little or no change in the tidal rise or fall over the HW portion of the tide curve). "

And they give further details in a pdf at: http://www.admiralty.co.uk/Admiralt.../Double high waters and high water stands.pdf
 
skip_mojo said:
As I don't think anyone answered your question directly, but its going to be confusing to many Solent sailors, it's worth noting that UKHO have updated approach to what 'HW' means in this case. Its not the single point of inflexion of the highest point of the tide, but can be the start or end of a HW stand in which there isn't a significant change. They've updated their FAQ and provided a document explaining this change:

The FAQ now states:
"This relates to a change in how the predictions are shown at the more complex ports along the south coast of the UK, in particular the Solent, based on customer feedback. It involves the identification of the start and end periods of High Water ‘Stands’ (i.e. the prolonged period of little or no change in the tidal rise or fall over the HW portion of the tide curve). "

And they give further details in a pdf at: http://www.admiralty.co.uk/Admiralt.../Double high waters and high water stands.pdf
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welcome.gif

Welcome to the forums and thanks for that information.
.
 
skip_mojo said:
As I don't think anyone answered your question directly, but its going to be confusing to many Solent sailors, it's worth noting that UKHO have updated approach to what 'HW' means in this case. Its not the single point of inflexion of the highest point of the tide, but can be the start or end of a HW stand in which there isn't a significant change. They've updated their FAQ and provided a document explaining this change:
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Thanks for that; excellent, clear and informative post!

As Vic says, welcome to the forum and definitely stick around :D:D
 
One might have one's own satellite feed from NASA, but if there's any doubt at all, you can't beat a slow recce' pass and watch which way the small foam bubbles are going at the proposed spot.

' The bubbles, always with the bubbles already ! ':)
 
dom said:
The UKHO's EasyTide website has been showing double HW readings for Portsmouth for a few days now. Any idea as to what's going on?
http://www.ukho.gov.uk/EasyTide/EasyTide/ShowPrediction.aspx?PortID=0065&PredictionLength=7
Click to expand...

They first started doing this a couple of months ago & it's bloody confusing.It approximates to the high water stand but if you just take the second reading at least where my boat is moored you can be seriously caught out because by the second hw reading it is dropping fast.
 
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