The weekend saw the highest astronomical tide of the year. However, it was even higher than predicted, and still is running above predictions.

https://www.ntslf.org/data/realtime?port=Newlyn

This is despite all the weather and sea conditions suggesting it should be below predictions. The local weather light winds (basically calm yesterday), fairly high barometric pressure. Local sea conditions, flat in Mount's Bay. Atlantic swell very small, so no wave setup surges. In fact, all the factors which increase tidal height were absent, all the normal factors which reduce it were present. I'd expected it to be 0.3-0.5m below predictions.

I was down at the Battery Rocks for a swim yesterday, and got chatting to a chap who had been a year long swimmer there most of his life. He'd never seen the tide so high in totally benign conditions.

No I'm baffled, as was the chap I spoke to, & I respect the opinion of people with his sort of observational experience. Mind you the sea is a mysterious thing.

Graham
Penzance

Graham Easterling wrote:

The weekend saw the highest astronomical tide of the year. However,
it was even higher than predicted, and still is running above
predictions.

https://www.ntslf.org/data/realtime?port=Newlyn

This is despite all the weather and sea conditions suggesting it
should be below predictions. The local weather light winds (basically
calm yesterday), fairly high barometric pressure. Local sea
conditions, flat in Mount's Bay. Atlantic swell very small, so no
wave setup surges. In fact, all the factors which increase tidal
height were absent, all the normal factors which reduce it were
present. I'd expected it to be 0.3-0.5m below predictions.

I was down at the Battery Rocks for a swim yesterday, and got
chatting to a chap who had been a year long swimmer there most of his
life. He'd never seen the tide so high in totally benign conditions.

No I'm baffled, as was the chap I spoke to, & I respect the opinion
of people with his sort of observational experience. Mind you the sea
is a mysterious thing.

Graham
Penzance

Sea level rise? Perhaps only apparent in calm conditions.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr

On Tuesday, September 22, 2020 at 11:20:01 AM UTC+1, Norman Lynagh wrote:
Graham Easterling wrote:

The weekend saw the highest astronomical tide of the year. However,
it was even higher than predicted, and still is running above
predictions.

https://www.ntslf.org/data/realtime?port=Newlyn

This is despite all the weather and sea conditions suggesting it
should be below predictions. The local weather light winds (basically
calm yesterday), fairly high barometric pressure. Local sea
conditions, flat in Mount's Bay. Atlantic swell very small, so no
wave setup surges. In fact, all the factors which increase tidal
height were absent, all the normal factors which reduce it were
present. I'd expected it to be 0.3-0.5m below predictions.

I was down at the Battery Rocks for a swim yesterday, and got
chatting to a chap who had been a year long swimmer there most of his
life. He'd never seen the tide so high in totally benign conditions.

No I'm baffled, as was the chap I spoke to, & I respect the opinion
of people with his sort of observational experience. Mind you the sea
is a mysterious thing.

Graham
Penzance

Sea level rise? Perhaps only apparent in calm conditions.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr

I don't think it's the whole story, experience has shown me that under recent conditions the actual tide is normally below predictions.

Mind you, over recent decades there has been a rise at Newlyn, which is supposed to be a stable site. (Though Scilly is sinking)

A study on sea level at Newlyn here
https://www.tandfonline.com/doi/full...ean%20w aters.

I can only assume that some weather event elsewhere in the north Atlantic has caused a 'dome' of water which has proved persistent.

Graham
Penzance

On Tuesday, September 22, 2020 at 11:28:21 AM UTC+1, Graham Easterling wrote:
On Tuesday, September 22, 2020 at 11:20:01 AM UTC+1, Norman Lynagh wrote:
Graham Easterling wrote:

The weekend saw the highest astronomical tide of the year. However,
it was even higher than predicted, and still is running above
predictions.

https://www.ntslf.org/data/realtime?port=Newlyn

This is despite all the weather and sea conditions suggesting it
should be below predictions. The local weather light winds (basically
calm yesterday), fairly high barometric pressure. Local sea
conditions, flat in Mount's Bay. Atlantic swell very small, so no
wave setup surges. In fact, all the factors which increase tidal
height were absent, all the normal factors which reduce it were
present. I'd expected it to be 0.3-0.5m below predictions.

I was down at the Battery Rocks for a swim yesterday, and got
chatting to a chap who had been a year long swimmer there most of his
life. He'd never seen the tide so high in totally benign conditions.

No I'm baffled, as was the chap I spoke to, & I respect the opinion
of people with his sort of observational experience. Mind you the sea
is a mysterious thing.

Graham
Penzance

Sea level rise? Perhaps only apparent in calm conditions.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr

I don't think it's the whole story, experience has shown me that under recent conditions the actual tide is normally below predictions.

Mind you, over recent decades there has been a rise at Newlyn, which is supposed to be a stable site. (Though Scilly is sinking)

A study on sea level at Newlyn here
https://www.tandfonline.com/doi/full...ean%20w aters.

I can only assume that some weather event elsewhere in the north Atlantic has caused a 'dome' of water which has proved persistent.

Graham
Penzance

Mind you, glancing through the article again (I first read it a couple of years back) One sentence
"However, the observed rate of sea level change at Newlyn over 1993–2014 has been much larger at 3.8 mm/year"

But I would have thought predicted levels take into account recent sea levels? I must read the whole article.

Graham
Penzance

On 22/09/2020 11:28, Graham Easterling wrote:
On Tuesday, September 22, 2020 at 11:20:01 AM UTC+1, Norman Lynagh wrote:
Graham Easterling wrote:

The weekend saw the highest astronomical tide of the year. However,
it was even higher than predicted, and still is running above
predictions.

https://www.ntslf.org/data/realtime?port=Newlyn

This is despite all the weather and sea conditions suggesting it
should be below predictions. The local weather light winds (basically
calm yesterday), fairly high barometric pressure. Local sea
conditions, flat in Mount's Bay. Atlantic swell very small, so no
wave setup surges. In fact, all the factors which increase tidal
height were absent, all the normal factors which reduce it were
present. I'd expected it to be 0.3-0.5m below predictions.

I was down at the Battery Rocks for a swim yesterday, and got
chatting to a chap who had been a year long swimmer there most of his
life. He'd never seen the tide so high in totally benign conditions.

No I'm baffled, as was the chap I spoke to, & I respect the opinion
of people with his sort of observational experience. Mind you the sea
is a mysterious thing.

Graham
Penzance

Sea level rise? Perhaps only apparent in calm conditions.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr

I don't think it's the whole story, experience has shown me that under recent conditions the actual tide is normally below predictions.

Mind you, over recent decades there has been a rise at Newlyn, which is supposed to be a stable site. (Though Scilly is sinking)

A study on sea level at Newlyn here
https://www.tandfonline.com/doi/full...ean%20w aters.

I can only assume that some weather event elsewhere in the north Atlantic has caused a 'dome' of water which has proved persistent.

Graham
Penzance


Although NTSLF uses supercomputer oceanographic processing of the first
pass MetO data, there are problems with it by the time it is output , if
not before.
Notoriously , www presentation so of no significance the likes of 07:60
instead of 08:00 for timings on their outputs.
Of more significance , if you look carefully at the archives, assuming
the same for Newlyn as for Southampton.
Coincident with change-over times of BST/GMT, over the week before and
after, there is a vertical "DC" offset in the mean sea level of about
0.15m, there until the next clocks change.
Unfortunately al loceanographic major processing uses Fortran still and
the people who developed the NTSLF tide predictor SW have retired, so mo
one to rectify its failings.
For Southampton it regularly fails to predict surges from the SSW, ie
wind that goes behind the Brest Peninsular and wind-stresses the water
betweem St Brieuc and IoW, worst case failing to predict about 0.8m surge.



--
Global sea level rise to 2100 from curve-fitted existing altimetry data
http://diverse.4mg.com/slr.htm

On Tuesday, September 22, 2020 at 11:46:24 AM UTC+1, N_Cook wrote:
On 22/09/2020 11:28, Graham Easterling wrote:
On Tuesday, September 22, 2020 at 11:20:01 AM UTC+1, Norman Lynagh wrote:
Graham Easterling wrote:

The weekend saw the highest astronomical tide of the year. However,
it was even higher than predicted, and still is running above
predictions.

https://www.ntslf.org/data/realtime?port=Newlyn

This is despite all the weather and sea conditions suggesting it
should be below predictions. The local weather light winds (basically
calm yesterday), fairly high barometric pressure. Local sea
conditions, flat in Mount's Bay. Atlantic swell very small, so no
wave setup surges. In fact, all the factors which increase tidal
height were absent, all the normal factors which reduce it were
present. I'd expected it to be 0.3-0.5m below predictions.

I was down at the Battery Rocks for a swim yesterday, and got
chatting to a chap who had been a year long swimmer there most of his
life. He'd never seen the tide so high in totally benign conditions.

No I'm baffled, as was the chap I spoke to, & I respect the opinion
of people with his sort of observational experience. Mind you the sea
is a mysterious thing.

Graham
Penzance

Sea level rise? Perhaps only apparent in calm conditions.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr

I don't think it's the whole story, experience has shown me that under recent conditions the actual tide is normally below predictions.

Mind you, over recent decades there has been a rise at Newlyn, which is supposed to be a stable site. (Though Scilly is sinking)

A study on sea level at Newlyn here
https://www.tandfonline.com/doi/full...ean%20w aters.

I can only assume that some weather event elsewhere in the north Atlantic has caused a 'dome' of water which has proved persistent.

Graham
Penzance


Although NTSLF uses supercomputer oceanographic processing of the first
pass MetO data, there are problems with it by the time it is output , if
not before.
Notoriously , www presentation so of no significance the likes of 07:60
instead of 08:00 for timings on their outputs.
Of more significance , if you look carefully at the archives, assuming
the same for Newlyn as for Southampton.
Coincident with change-over times of BST/GMT, over the week before and
after, there is a vertical "DC" offset in the mean sea level of about
0.15m, there until the next clocks change.
Unfortunately al loceanographic major processing uses Fortran still and
the people who developed the NTSLF tide predictor SW have retired, so mo
one to rectify its failings.
For Southampton it regularly fails to predict surges from the SSW, ie
wind that goes behind the Brest Peninsular and wind-stresses the water
betweem St Brieuc and IoW, worst case failing to predict about 0.8m surge..



--
Global sea level rise to 2100 from curve-fitted existing altimetry data
http://diverse.4mg.com/slr.htm

As I mentioned on UK Weather and Climate group, the unusual high tides, above astronomcal, timed at spring tide are probably a bit of extra swell. Maybe from the rather numerous Atantic hurricanes. The forecast models don't cope well with rogue waves nevermind rogue swells. Non linear interactions, unusual wave trains and all that. Notice the amplitudes are the same as astronomical.

Len
Wembury

On 23/09/2020 15:03, wrote:
On Tuesday, September 22, 2020 at 11:46:24 AM UTC+1, N_Cook wrote:
On 22/09/2020 11:28, Graham Easterling wrote:
On Tuesday, September 22, 2020 at 11:20:01 AM UTC+1, Norman Lynagh wrote:
Graham Easterling wrote:

The weekend saw the highest astronomical tide of the year. However,
it was even higher than predicted, and still is running above
predictions.

https://www.ntslf.org/data/realtime?port=Newlyn

This is despite all the weather and sea conditions suggesting it
should be below predictions. The local weather light winds (basically
calm yesterday), fairly high barometric pressure. Local sea
conditions, flat in Mount's Bay. Atlantic swell very small, so no
wave setup surges. In fact, all the factors which increase tidal
height were absent, all the normal factors which reduce it were
present. I'd expected it to be 0.3-0.5m below predictions.

I was down at the Battery Rocks for a swim yesterday, and got
chatting to a chap who had been a year long swimmer there most of his
life. He'd never seen the tide so high in totally benign conditions.

No I'm baffled, as was the chap I spoke to, & I respect the opinion
of people with his sort of observational experience. Mind you the sea
is a mysterious thing.

Graham
Penzance

Sea level rise? Perhaps only apparent in calm conditions.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr

I don't think it's the whole story, experience has shown me that under recent conditions the actual tide is normally below predictions.

Mind you, over recent decades there has been a rise at Newlyn, which is supposed to be a stable site. (Though Scilly is sinking)

A study on sea level at Newlyn here
https://www.tandfonline.com/doi/full...ean%20w aters.

I can only assume that some weather event elsewhere in the north Atlantic has caused a 'dome' of water which has proved persistent.

Graham
Penzance


Although NTSLF uses supercomputer oceanographic processing of the first
pass MetO data, there are problems with it by the time it is output , if
not before.
Notoriously , www presentation so of no significance the likes of 07:60
instead of 08:00 for timings on their outputs.
Of more significance , if you look carefully at the archives, assuming
the same for Newlyn as for Southampton.
Coincident with change-over times of BST/GMT, over the week before and
after, there is a vertical "DC" offset in the mean sea level of about
0.15m, there until the next clocks change.
Unfortunately al loceanographic major processing uses Fortran still and
the people who developed the NTSLF tide predictor SW have retired, so mo
one to rectify its failings.
For Southampton it regularly fails to predict surges from the SSW, ie
wind that goes behind the Brest Peninsular and wind-stresses the water
betweem St Brieuc and IoW, worst case failing to predict about 0.8m surge..



--
Global sea level rise to 2100 from curve-fitted existing altimetry data
http://diverse.4mg.com/slr.htm

As I mentioned on UK Weather and Climate group, the unusual high tides, above astronomcal, timed at spring tide are probably a bit of extra swell. Maybe from the rather numerous Atantic hurricanes. The forecast models don't cope well with rogue waves nevermind rogue swells. Non linear interactions, unusual wave trains and all that. Notice the amplitudes are the same as astronomical.

Len
Wembury


I somehow thought Newlyn opened onto the Atlantic . Looking at a map I
see it opens on to the Eng Channel so the higher tides was simply the
east-west surge moving along the Channel over the weekend, as in
Plymouth. Weymouth, Southampton etc , due to the east wind over the
weekend. NTSLF "surge predictor" not accounting for it, well nothing new
there. Oddly it does very well at predicting delayed surges from strong
WNW wind passing over Southampton (causing immediate local negative
surge) and the positive surge reflecting off the Pas de Calais coast
back to the Solent.

--
Global sea level rise to 2100 from curve-fitted existing altimetry data
http://diverse.4mg.com/slr.htm

On 22/09/2020 10:21, Graham Easterling wrote:
The weekend saw the highest astronomical tide of the year. However, it was even higher than predicted, and still is running above predictions.

https://www.ntslf.org/data/realtime?port=Newlyn

This is despite all the weather and sea conditions suggesting it should be below predictions. The local weather light winds (basically calm yesterday), fairly high barometric pressure. Local sea conditions, flat in Mount's Bay. Atlantic swell very small, so no wave setup surges. In fact, all the factors which increase tidal height were absent, all the normal factors which reduce it were present. I'd expected it to be 0.3-0.5m below predictions.

I was down at the Battery Rocks for a swim yesterday, and got chatting to a chap who had been a year long swimmer there most of his life. He'd never seen the tide so high in totally benign conditions.

No I'm baffled, as was the chap I spoke to, & I respect the opinion of people with his sort of observational experience. Mind you the sea is a mysterious thing.

Graham
Penzance


No mystery to us in Southampton. The (one-time) best tide predictions
for Southampton was the Admiralty/UKHO as they've been doing it for 160
years. Either its GIGO (updating with known erroneous VTS tide gauge
data ) or failing to update since recent extensive dredging for the
passage of the largest container ships in otherwise shallow water.
It got so bad that for a covid lockdown project I've developed my own
tide-curve for Southampton.
Details at top of my page
http://diverse.4mg.com/solent.htm
NTSLF uses up to 240 harmonic constants of NOC/Admiralty Poltips
software. My "Belsize" tide curve currently, updated daily, now using
218 harmonic constants, 4.0cm RMS error to normalised (removing inverse
barometer/surges/seiches) to 1483 datapoints and almost always
favourable cross-comparisons with the big-boys .
I've not checked other ports for NTSLF tide predictions but if
deep-water port predictions for the likes of Newlyn are awry then
probably they're relying on very old data. With recent decades extra sea
level rise , that must be starting to affect the tide strreams and hence
tides around the UK.


--
Global sea level rise to 2100 from curve-fitted existing altimetry data
http://diverse.4mg.com/slr.htm

No mystery to us in Southampton.

It's a mystery to me, as it's very different to what I'd expect based on years of observation & the prevailing weather & sea conditions, which are particularly significant here with the wave setup conditions we experience, and the shape of the Bay making it very wind affected as far as tidal height is concerned.

Graham
Penzance

On 22/09/2020 11:37, Graham Easterling wrote:



No mystery to us in Southampton.

It's a mystery to me, as it's very different to what I'd expect based
on years of observation & the prevailing weather & sea conditions,
which are particularly significant here with the wave setup
conditions we experience, and the shape of the Bay making it very
wind affected as far as tidal height is concerned.

It is just after the new moon and at an equinox so the geometry is just
about perfect for seeing maximum tidal range. I am at a bit of a loss as
to why it should occur a couple of days after new moon though. Thursday
was perfect new moon and Friday 18/9 was the moon at closest approach.

I guess it is the difference between theory (uniform ocean on a perfect
sphere) and reality with all those nasty continents and coastlines
about. I have the astronomical tidal coefficients somewhere and will dig
it out to see if there was anything particularly unusual.

Do you have tidal curves for 17/9-21/9 ? I'd be interested to see them.

16/10 also has favourable geometry for a good high tide as well.

--
Regards,
Martin Brown