Strange tidal behaviour in a Pembrokeshire harbour may have been the result of the rare 'meteotsunami' phenomenon.
Married couple Charles and Claire Davies, whose house overlooks Solva harbour, noticed something odd at around 8.50am on Saturday, when there should still have been around an hour until high tide. "The water appeared to be running out of the harbour rather than in," Charles told WalesOnline. "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, 69, 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.
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"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 his 13 years living in the area, he had never seen anything like it. And there appeared to be no reports of similar activity that morning anywhere other than this small spot of Pembrokeshire coastline.
But then one of Charles' family members came across an Irish Times article about a tidal event which happened at 2pm on the same day and left west Cork 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". He added: "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 meteotsunami — large waves driven by disturbances in air pressure, often linked to extreme weather events. The oceanographer Dr Gerard McCarthy told the Irish Examiner that Courtmacsherry was regularly affected by seiching, an oscillation of tidal currents — "basically water moving backwards and forwards".
He added: "My best guest 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 believed 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.
Channel 4 News' Andy Davies — cousin to Charles — shared a conversation he had with meteotsunami expert Dr Julian Thompson about the Solva event. Andy tweeted: "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!'"
WalesOnline has approached the Met Office for more details on the potential causes.
You can read more Pembrokeshire news here.
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