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Once again, Portugal and Spain find themselves dealing with the consequences of extensive flooding after Storm Claudia delivered torrential downpours and strong winds the previous week.

Claudia's Formation and Trajectory

This weather system originated from a region of depressed atmospheric pressure that had beforehand caused early season chilly and snowy weather through the eastern sectors of the Canadian territory and the north-eastern US in early November.

Claudia moved eastward across the Atlantic Ocean during the second weekend of November before losing momentum and stopping to the northwestern area of the Iberian peninsula, trapped within a trough of an ever more meandering atmospheric river.

Effects in the Iberian Peninsula

Spain's Galicia area in the northwest was initially impacted, with three to six inches of rain coming down along its western coastline in just one full day up to Wednesday evening as a slow-moving band of rain drifted across the western areas of the region.

Further showers and thunderstorms on the following Thursday led to floods to Portuguese localities where an older couple died in Lisbon after floodwaters from the swollen Tagus entered their home as they rested.

Unsettled atmospheric states lasted through the weekend, with a tornado ripping through a campsite and a adjacent hotel in the town of Albufeira in the Algarve region on Saturday last week, fatally injuring an British woman aged 85 and wounding 28 people.

Broader Impacts across the European continent

Claudia had more extensive impacts across Europe's western part. By pulling tropical air from the warmer regions, the system contributed to thermometers climbing in south-west France to 85.6 degrees Fahrenheit, the nation's all-time high late autumn reading.

By Friday, this hot and moist atmospheric body clashed with a cold air mass across the northern areas of Europe, generating a rainfall belt extending from the west of Ireland to the Russian Federation.

In the United Kingdom, this halting system of rain brought record-breaking rain accumulations, causing major inundations in the principality of Wales.

As this weather phenomenon loses strength early this week, the frigid air will advance southward, giving Europe its initial glimpse of colder weather.

Simultaneous Occurrences in California

California encountered a so-called atmospheric river last week, delivering intense precipitation and strong winds that resulted in rapid flooding and debris flows in areas affected by wildfires earlier this year.

More than 50mm of rain fell in the southern region of the state on the week's end, with a additional two inches broadly over the state on the subsequent Saturday.

In excess of 100 millimetres of rain accumulated over shoreline regions of Southern CA in all, attaining a full 200 millimetres in locations at higher elevations.

An atmospheric river is a plume of warm, moist air originating from the tropical or subtropical regions.

Regions previously burned including Pacific Palisades and Altadena region suffered the worst of the sudden floods and landslides, forcing residents to flee.

Elsewhere in California, a man in his seventies lost his life after his car was washed off a inundated overpass, and a young girl aged seven and her dad were swept into the sea by powerful waves on the Central Coast.