The 'extraordinarily powerful' surges were captured by Charles and Claire Davies
Unusual tidal behaviour in Pembrokeshire may have been the result of a rare phenomenon called a 'meteotsunami', experts say.Charles and Claire Davies, whose home overlooks the harbour in Solva, noticed something strange at around 8.50am on Saturday (June 19), one hour before high tide.
"The water appeared to be running out of the harbour rather than in," Charles said. "We started to see this strange event where the water was surging in and out and in again. This happened a number of times over the next quarter of an hour."The retired engineer added: "There was a gentle north-easterly wind, the trees were hardly moving, it was a lovely sunny day. We expect surges during storm conditions but we've never seen one during benign conditions.
"We saw water coming in at seven knots, going back out again and causing boats to lean quite dramatically. It was causing an area of swirling water, a back eddy around the little headland.
"If there were people in the water swimming or in kayaks, it would have been quite a serious event to them, because an Olympic swimmer swims at five or six miles an hour and this water was moving considerably faster than that, I would say. They wouldn't have been able to keep up with it."
Charles said the "extraordinarily powerful" surges died down after about 15 minutes.
In more than a decade of living in the area, Charles said he has never seen anything like it.
There appeared to be no reports of similar activity that morning anywhere other than this small spot of Pembrokeshire coastline.
Until the Irish Times published an article about a tidal event which happened at 2pm on the same day in west Cork, leaving residents baffled.
One charter boat operator at Courtmacsherry harbour told the newspaper he could see the water was "going the wrong way, it should have been coming in".
'The first thing you think is - tsunami'
The boat operator said: "The water was rushing out like a river. I’d never seen anything like it before. The first thing you think is ‘tsunami’ and to be honest if it was going any faster I think we all would have been heading for the hills.”
Experts believe the activity may have been caused by a rare phenomenon called a meteotsunami - large waves driven by disturbances in air pressure, often linked to extreme weather events.
Dr Gerard McCarthy, an oceanographer, told the Irish Examiner that Courtmacsherry was often affected by seiching, which is an oscillation of tidal currents - "basically water moving backwards and forwards".
Dr McCarthy added: "My best guess is that this regular seiching coincided with a dramatic and sudden change in atmospheric pressure somewhere out over the Atlantic off the coast of west Cork.
"If you imagine someone dropping a large volume of water straight down on the sea, that’s the kind of effect we are talking about. That pressure combined with the regular to and fro of water in those bays could have created a dramatic and unusual effect like the one we saw.”
The expert believes the same atmospheric event was the likely cause of the Solva activity.
"It definitely had an impact, though less severe, further along the Irish coast in Wexford and there is also evidence of it being felt in Wales and Cornwall so this was quite a significant event," he said.
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Channel 4 News' Wales Correspondent Andy Davies, who is cousin to Charles, shared a conversation he had with another meteotsunami expert, Dr Julian Thompson, about the Solva event.
Andy said on Twitter: "He's watched the wider footage and thinks a storm surge or a meteotsunami are 'the two prime candidates'. He thinks the tidal event along the Irish coast is 'probably' linked to what happened in Solva. Says there are fewer than 10 meteotsunamis on average per year witnessed around the UK — areas most prone: south west corner of Wales to Isle of Wight and northern part of the North Sea."The correspondent added: "Dr Thompson says it's not clear whether meteotsunamis are increasing in frequency [as recording of them only dates back 20-25 years] but documenting where they happen is an important public safety measure given the suddenness with which they can emerge.
"Anyway, I found it all very intriguing — Dr Julian Thompson says he's now referred this to the Met Office to investigate further to establish whether it's a) a storm surge b) a meteotsunami or c) 'something else in which case we hold hands up and say: we don’t know!'"