The Strangford Narrows

Alan Mckewan · 01 November 2001, 19:14

Following on from the Menai Straights thread.
The Strangford Narrows are at the entrance to Strangford Lough on the East coast of N.I. just to the west of the south end of the Isle of Man. Strangford Lough is a tidal inland lough about 15 miles long and all the tide flows in and out through the narrows between the towns of Portaferry and Strangford. Spring tides flow either way at 8-10 knots at the narrowest point. There are two interesting effects.
Firstly the narrows flow out to the south-southwest and the prevailing winds are straight up the Irish sea from the southwest. On a spring ebb in a (very common) strong southwesterly you get huge, very short seas at the "bar" - typically 10m apart and 6m+ high. A real problem in a rib! (or other planing boat). The tide in Strangford is also two hours behind the Irish sea, so you get the "falling off the end" effect to make things worse. The IOM guys are often faced with this when heading home (comments please).
Secondly the lough receives lots of river and rainwater into it, so the water is somewhat less saline than the sea outside. So on an ebb tide at the bar when the less salty water meets the more salty water, the outgoing flow goes "underneath" the standing water, taking with it loads of air in rougher weather, and forming a huge standing wave, like stepping off a 2-3m waterfall. I have gone out in a yacht at half tide and the boat sinks almost to the gunnels in the bubbly water as the density of the water/air mixture is much less than ordinary water. It is very frightening!

(Probably less of a problem in a rib).

sirzap · 01 November 2001, 21:20

Visual Aid...

Keith Hart · 03 November 2001, 16:50

Wow Alan, that sounds really spectacular, thanks.

I remember a few years ago standing on the North mainland of Orkney and looking out onto Eynhallow Sound which is between Orkney mainland and the island of Rousay. In the midle of the sound, which is about 1 mile across, is a small island called Eynhallow (hence the name of the sound). I could see a large standing wave tumbling onto itself rather fiercely. As the tide overcame the current (or vice versa) the wave bowed out and after a while the bow was broken and the current rushed through. It looked VERY frightening.

When I lived on Orkney (believe it or not I was a policeman up there - the polis as we were known) a small rowing boat with two persons on board was crossing the sound and was capsised. The bodies were never found. Well, the remains of one (minus head) was washed up months later somewhere by John O'Groats. I was told that the boat was sucked down in a whirlpool!

I have also flown over the Pentland Firth many times and have looked down is astonishment at the 'boiling' waters and whirlpools. I did cross in a force 8 gale once in the short sea route ferry from John O'Groats, which in those days was an old 40 foot boat. The hatches were battened down and a 45 minuite journey took 2.5 hours. In the same storm a fishing boat went down North of Orkney and 5 persons were drowned (and still I wanted a boat of my own).

All this and they have CLOSED the Coastguard post on Orkney!

Does anyone know these stretches of water and what they are like to sail in a rib?

Keith Hart

Alan Mckewan · 03 November 2001, 21:54

We went across the Penland Firth in July and it was totally flat!
Anyway all this talk of whirlpools and so on really begs for someone to describe the UK "ultimate" - the gulf of Corryvreckan. This stretch of water is in the western isles of Scotland just below Oban. I've been past it a few times but is there anyone out there who can enlighten us?

sirzap · 03 November 2001, 22:28

Corryvreckan located between Scarba and Jura in Argyll and Bute
LAT 56.15* N
Long 5.73* W

sirzap · 03 November 2001, 22:43

I believe we were in the area when this photo as taken...not having a chart avalible at the time

... but there was a strong current and many small whirl pools were visible...

sirzap · 03 November 2001, 22:57

a good article...
http://www.smithsonianmag.si.edu/jou...ll_page_1.html

Keith Hart · 04 November 2001, 06:13

Thanks Sirzap, however a correction 'a VERY good article'....

I can confirm that the 'Whirlpool' is on the os map. Take a look:

http://www.streetmap.co.uk/streetmap...=702500&zoom=3

Keith Hart

Rannsachair · 05 November 2001, 07:16

Fascinating place - best seen during a Spring tide. Though different evry time you see it!

If you are in the area, I can recommend a trip from Crinan, plus more information on:

http://www.gemini-crinan.co.uk/corryvreckan.html

There was a recent documentary filmed there last year by Equinox - was out there during the filming.

George Orwell lived next to it on Jura, and nearly drowned in it:

http://www.smithsonianmag.si.edu/jou...01/orwell.html

Brian · 07 November 2001, 15:31

Fascinating stuff Alan-an an excellant start to what I hope is an interesting series of threads.
Yes to the Corryvreckan-who knows it well and can describe it?
According to my charts it is a very large area that is susceptable to maelstrom and not just one small place. Is this correct?
Also, how about Ramsey Sound and possibly Jack Sound, slightly to it's South (both just North of Milford Haven, S. Wales).
I've been through both but obviously at a very benign time. The video, Extreme RIBs has some excellent footage of Ramsey in an "interesting" mood, but what is the advice given to those who venture thereabouts?

Alan Priddy · 07 November 2001, 21:48

All nice areas for a bit of fun, but for real overfalls and wet pants try Muckle Flugga ( Top end of Shetlands) or Bishops Rock (western end of Scillies) Failing that, Cap Finistare is interesting along with Cape Fear at the Southern end of Greenland. Both of these headlands live up to their names. Mind you 2 miles offshore of Portland Bill can be interesting on a bad day to say the least!

Keith Hart · 07 November 2001, 21:58

Okay Alan, appetites well and truly whetted. Now tell us about them please.

Keith Hart

Brian · 14 November 2001, 16:04

Nobody answered my question about the Corryvreckan...is it one big whirlpool or are there lots of them and when does it/they occur. Look at this chart segment to see what I mean...

Rannsachair · 14 November 2001, 19:27

Brian,

It is not just a large single whirlpool - though it is generated by vortices from a single pinacle of rock, the vortices vary in strength and move with the current.

I have pinched the following from:

Gemini Cruises
"A brief outline of how the 'whirlpool' works follows. 'Maelstrom' would be a better description.

The whole of the Sound of Jura is a tidal anomaly. The tide is low in Lochgilphead when the tide is high in Crinan. It is absolutely diametrically opposed.

This is curious when only six miles separate the two, on land at least. However, the Mull of Kintyre, a peninsula over sixty miles long, forms a wall opposite the island chain formed by Islay, Jura, Scarba, Lunga and Rubha Fiola.

As the tide ebbs south past the gaps between these islands, it sucks the tide up the Sound of Jura, flooding and rising north. It then flows west, out through the Corryvreckan, The Grey Dog and north through Fladda.

The maelstrom in the Corryvreckan works differently when the tide is ebbing from when it is flooding.

On the ebb, water is flowing in relatively undisturbed from the open sea.

On the flood, water has flowed up the Sound of Jura and has been agitated by the topography of the seabed.

There are innumerable humps and holes and reefs in the Sound and these create terrific tidal flows, up-thrusts and eddies all over the place until finally in the Gulf there is a huge hole down to 219 metres before being confronted by a pinnacle of rock off the Scarba shore which rises to 29 metres from the surface.

The steep east face of the pinnacle forces a massive upthrust of water to surface in pulses which are then swept away westward by the tidal flow and these dissipate into vortices or whirlpools moving west.

This is all clearly visible when there is no wind and the turbulent patterns are fascinating to see in mirror calm conditions.

However when there is any serious wind strength, particularly from the west, the up-thrusts at the pinnacle fold into the oncoming waves and accentuate them. Thus building, in gale force conditions, standing waves that can be 8, 10 or 15 feet high. A truly awesome sight!

When the wind is from the South East or from N or E of North, then the Gulf is in the lee and it tends to be less rough - one can see the pure tidal turbulence. The relative state of Springs to Neap tides also affects the strength of the flows and hence turbulence. So as you can imagine there are many, many factors which affect the performance and so one can never be entirely sure how it will be behaving before one gets there. "

It is a very special place and well worth a visit.