Tides

[Iliade]

So, this is the second time in the last month that I have gone to the boat with the intention of quickly moving her to a walk-on berth to load some awkward stuff, only to find that the water was a good 1 - 0.75 m less than the Admiralty said it was going to be and I have had to start pumping/rowing

To the best of my knowledge this is a recent phenomenon as it has never really caught me out before.

Yes, there is a bit of a blow some way to the west of us, but not enough to suggest such a large storm drop. Our pressure today was 1015 hPa, so pretty blooming close to Standard Pressure.

Any ideas?

 

[maby]

1m seems to be too big an error to explain as meteorological! Are you sure that you have the times consistent throughout? A couple of weeks ago I experienced a similar discrepancy around the Solent between the depths calculated on my phone and real life - only to discover that my phone was still working in BST...

 

[VicS]

So, this is the second time in the last month that I have gone to the boat with the intention of quickly moving her to a walk-on berth to load some awkward stuff, only to find that the water was a good 1 - 0.75 m less than the Admiralty said it was going to be and I have had to start pumping/rowing

To the best of my knowledge this is a recent phenomenon as it has never really caught me out before.

Yes, there is a bit of a blow some way to the west of us, but not enough to suggest such a large storm drop. Our pressure today was 1015 hPa, so pretty blooming close to Standard Pressure.

Any ideas?

Pretty close to predicted at both Portsmouth and Newhaven today , See UK National Tide Gauge Network

 

[Iliade]

I looked at SHM's entry there this morning while sitting on the mud. Annoyingly it was some six hours out of date and also referenced OS datum rather than LAT so was a little unhelpful.

The height that I am interested in is 4m rise of tide, i.e. not far from the time when the gradient of the tidal height starts to get really steep. It only needs to shift by half an hour and most of that water has gone.

As I said, it is not usually wrong...

 

[Iliade]

1m seems to be too big an error to explain as meteorological! Are you sure that you have the times consistent throughout? A couple of weeks ago I experienced a similar discrepancy around the Solent between the depths calculated on my phone and real life - only to discover that my phone was still working in BST...

Yes, I checked because I feared that could be the case. I was comparing Easytide and my Garmin plotter's tidal prediction with the no longer submerged mud outside (and my watch/phone which are both tied to GPS time)

 

[Buck Turgidson]

Yes, I checked because I feared that could be the case. I was comparing Easytide and my Garmin plotter's tidal prediction with the no longer submerged mud outside (and my watch/phone which are both tied to GPS time)

Not sure if the admiralty has much to do with Easytide or Garmin. I recently had a large(%) difference between the tide on two different apps and the one I calculated from the almanac. (secondary port). My manual calculation was correct which was lucky as I was doing my Yachtmaster exam at the time!!!

 

[Yellow Ballad]

I have no idea of your local conditions but could it be silting?

 

[Iliade]

The silting here is very bad, but not the (main) issue. Indeed my berth would be uncomfortably scary without all the mud to help keep the boat upright!

Easytide is credited to UKHO & Admiralty: Show Prediction (free) - SHOREHAM 07/01/2020 for 1 day - EasyTide

I am a mile or so up the river, but that usually retards the tide a little, rather than advancing it.

Shoreham is a primary/standard port with its own tide gauge, albeit it's an old one.
http://westviewsailing.co.uk/wp-content/uploads/2018/02/YMSecondary-Ports-Oct14.pdf

Looking at the Newhaven plot there is an advance on the falling tide (5th-6th) giving about 25cm discrepancy, maybe that was more pronounced at SHM, or at least up the river it was, but why did it happen?

Oh, and look at the surge this morning! There are flood warnings here, but I think they are over egging a bit: Monitoring Station Information for Shoreham Harbour | Flood Assist Insurance




I just found this site which gives current tidal report for SHM River Adur at Shoreham Harbour: River level and flood alerts

I previously only knew of the Environment agency's site which was hours old data.

I wonder if it was a storm skew? : What is a storm surge? | eSurge Web Portal