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Portugal and Spain are once more dealing with the consequences of widespread flooding after Storm Claudia unleashed torrential downpours and strong winds last week.

Claudia's Formation and Trajectory

The storm system developed from a region of depressed atmospheric pressure that had previously ushered in early season cold and snowy conditions through the eastern sectors of the Canadian territory and the north-eastern United States in early November.

This storm tracked eastwards across the Atlantic in the middle of the second week of November before decelerating and halting to the north-west of the Spanish and Portuguese landmass, snared in a dip of an increasingly amplified jet stream.

Effects in Spain and Portugal

Galicia in north-west Spain was initially impacted, with a substantial 80 to 150 millimetres of rain coming down along its western coastline in just 24 hours up to the evening of Wednesday as a leisurely moving system of rain pushed across western parts of the peninsula.

Further showers and thunderstorms on the following Thursday led to floods to Portuguese localities where a senior pair perished in Lisbon after floodwaters from the swollen Tagus invaded their residence as they were asleep.

Unsettled atmospheric states lasted through the weekend, with a tornado tearing through a outdoor lodging area and a adjacent hotel in the town of Albufeira in Portugal's south on Saturday, killing an elderly British lady and harming 28 people.

Wider Effects across the European continent

Claudia had wider effects across the western European nations. By drawing warm air from the subtropical zones, the system assisted in raising temperatures in southwestern France to 85.6 degrees Fahrenheit, the nation's all-time high autumn temperature.

By the following Friday, this warm and humid air mass clashed with a chilly atmospheric body across the northern regions of the continent, forming a band of rain stretching from Ireland's west to Russia.

In the UK, this stalling band of rain produced exceptionally large precipitation amounts, causing major inundations in Wales.

As this weather phenomenon loses strength at the start of the week, the chilly atmospheric system will push south, providing the continent its first taste of the winter season.

Related Incidents in California, USA

The Golden State experienced a so-called atmospheric river the previous week, bringing intense precipitation and high-velocity gusts that resulted in rapid flooding and landslides in regions scarred by forest fires earlier this year.

In excess of 50 millimetres of rain fell in southern California on last Friday, with a further 50mm widely across the state on Saturday last.

In excess of 100 millimetres of rain fell over shoreline regions of the state's south in total, attaining eight inches in total in locations at higher elevations.

An atmospheric river is a concentrated stream of tropical, saturated air coming from the tropical or subtropical regions.

Locations with fire damage including the Pacific Palisades area and Altadena endured the most severe the sudden floods and landslides, prompting evacuations.

Across California, a man in his seventies passed away after his vehicle was washed off a flooded bridge, and a child of seven years and her dad were pulled into the ocean by powerful waves on the the state's central shoreline.