Strong winds and high water levels created unusually mighty waves on the Baltic Sea overnight, measuring around 8.2 metres in significant wave height according to Finland's weather institute.
Significant wave height is a measurement calculated as the mean of the highest third of waves over a period, comparable to the average of 15-20 waves over a period of around ten minutes.
But several individual waves were far higher than that, according to data sent by one of the Finnish meteorological institute's automated buoys measuring wave height in the Gulf of Bothnia.
One registered at around midnight measured 14.8 metres, the agency said on Twitter.
— Ilmatieteen laitos (@meteorologit) January 12, 2017
The figure has not yet been confirmed as accurate, but it could be the highest wave ever measured in the Baltic Sea. The previous record is from December 22nd 2004, when one wave reached a height of 14 metres. The significant wave height then was 8.2 metres, just as last night.
The highest wave measured by a buoy was a 19-metre behemoth recorded in the North Atlantic between Iceland and the United Kingdom in December, according to the World Meteorological Organization.
Several incidents caused by the storm were reported across southern Sweden on Wednesday and Thursday, both at land and at sea.
Passengers on the Tallink Silja ferry Romantika reported that a radar antenna had come off and water had been leaking into their cabins on their journey between Stockholm and Riga, Latvia.
A veterinarian was called out to examine two horses when another Tallink Silja ferrry from Helsinki reached Stockholm early on Thursday morning. The animals were said to have been in poor condition, reported the Expressen tabloid, but had no other updates in the afternoon.