Communities across California received evacuation warnings last week as heavy rainfall triggered significant flood and landslide risks across the state. The severe weather conditions have been attributed to an atmospheric river phenomenon, creating dangerous conditions along coastal regions.
Atmospheric River Phenomenon Explained
The storms battering the United States' western coast originate from what meteorologists call an "atmospheric river" - a long, concentrated filament of moisture-saturated air that forms above the Pacific Ocean. While these weather systems play a crucial role in replenishing reservoirs and building snowpack in California, they can also deliver destructive volumes of rain that overwhelm infrastructure and trigger natural disasters.
Global Weather Extremes Intensify
Meanwhile, other regions experienced contrasting weather extremes. In Japan, the high-altitude town of Sukayu on Honshu island recorded more than 1 metre of snowfall, with the intensity and timing breaking seasonal records for early winter. Heavy snow also affected parts of Hokkaido, Japan's northernmost island.
Australia faced its own weather challenges as severe thunderstorms swept across northern and eastern regions. Last Friday alone, over 11,000 homes lost power due to intense weather conditions featuring heavy rain, hail and strong winds. The storms were fuelled by humid tropical air moving from northern regions, creating additional hazards including bushfires triggered by lightning strikes in New South Wales plains.
Contrasting Conditions Across Continents
The weather patterns presented striking contrasts between regions. While California battled excessive rainfall, parts of Colorado experienced unusually warm conditions with Denver recording its highest ever November temperature of 28C. The city also surpassed its third-latest snowfall date this year, forcing ski resorts to delay openings until December.
Europe didn't escape the extreme weather pattern, with Italy experiencing tragic consequences from heavy rainfall. Mudslides in northern Italy resulted in two fatalities after the Torre River overflowed its banks. The river burst following approximately 25cm (10 inches) of rainfall within an eight-hour period, causing significant flooding in Brazzano di Cormons town and forcing about 300 residents in nearby Versa hamlet to evacuate.
The simultaneous occurrence of these diverse extreme weather events across multiple continents highlights the increasing volatility in global weather patterns that communities worldwide must now confront.
