Storm Dennis hit several western European countries over the weekend with very heavy rain and hurricane-force winds. Minimum central air pressure of 920 hPa was recorded on Saturday, February 15, making it the second-strongest North Atlantic extratropical cyclone since records began more than 150 years ago; just 7 hPa short of the all-time North Atlantic record, set by the Braer Storm of 1993.
The storm left at least 2 people dead in the United Kingdom, dumped more than a month’s worth of rain on South Wales, prompted the UK Environment Agency to issue a record number of flood warnings for one day, and caused widespread severe flooding across parts of the country. A yellow wind warning was still in place across the north and west of the UK on Monday, February 17. It also affected Belgium, Netherlands, Germany, northern Spain, and France.
Dennis caused huge waves and hurricane-force winds, with wind gusts in Iceland reaching 256 km/h (159 mph) on Friday.
The average wave heights in the North Atlantic were around 12 to 18 m (40 to 60 feet), but the largest waves easily topped 30 m (100 feet).
In South Wales, winds of more than 150 km/h (90 moh) were registered in Aberdaron, while more than 127 mm (5 inches) of rain fell which was a little more than what the area usually receives for the whole month of February. This resulted in flooding that prompted numerous evacuations, even cutting off several communities.