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Once again, Portugal and Spain find themselves dealing with the consequences of extensive inundation after Storm Claudia unleashed heavy rain and powerful gusts last week.

The Storm's Genesis and Journey

The storm system developed from an area of low pressure that had earlier caused unseasonably early chilly and snowy weather through the eastern sectors of Canada and the north-eastern US in early November.

This storm journeyed east across the Atlantic Ocean in the middle of the second week of November before slowing and stalling to the north-west of the Spanish and Portuguese landmass, trapped within a trough of an ever more meandering jet stream.

Effects in Spain and Portugal

Spain's Galicia area in the northwest was the first affected, with three to six inches of rain coming down along its western coastline in just 24 hours up to Wednesday night as a slow-moving band of rain crawled across western parts of the region.

Further showers and thunderstorms on the following Thursday brought flooding to areas in Portugal where an elderly couple died in the capital Lisbon after water from the overflowing Tagus River invaded their residence as they were asleep.

Tempestuous weather lasted through the weekend, with a tornado ripping through a campsite and a close-by inn in Albufeira in Portugal's south on Saturday last week, claiming the life of an 85-year-old British woman and injuring two dozen and eight persons.

Extended Consequences across the European continent

Claudia had wider effects across western Europe. By siphoning heated air from the warmer regions, the system assisted in raising temperatures in southwestern France to nearly 30 degrees Celsius, the country's highest recorded autumn temperature.

By Friday, this warm and humid air mass met a frigid air system across the northern regions of Europe, creating a band of rain extending from Ireland's west to Russia.

In the Britain, this stalling band of rain delivered very high rainfall totals, leading to severe flooding in the principality of Wales.

As this weather phenomenon progressively weakens early this week, the frigid air will move towards the south, providing the continent its premier experience of colder weather.

Parallel Events in California

California experienced a so-called atmospheric river the previous week, causing heavy rain and powerful winds that resulted in rapid flooding and debris flows in areas impacted by wildfires previously in the year.

More than 50mm of rain was recorded in California's southern part on the week's end, with a another 50 millimetres widely across the state on Saturday last.

In excess of 100 millimetres of rain accumulated over shoreline regions of southern California in aggregate, reaching 200mm overall in areas of elevated terrain.

An atmospheric river is a narrow band of hot, humid air coming from the tropical or subtropical regions.

Locations with fire damage including the Pacific Palisades area and Altadena region endured the worst of the sudden floods and mudslides, prompting evacuations.

Across California, a man in his seventies passed away after his car was washed off a submerged bridge, and a young girl aged seven and her dad were pulled into the sea by powerful waves on the California's Central Coast.