Deadly Bomb Cyclone Triggers Power Outages for Thousands in US North-West

A severe storm originating off the coasts of the US north-west and western Canada is impacting the region, delivering high winds, flooding, and snow to more than seven million residents in states bordering the Pacific Ocean. This weather system has led to extensive power disruptions and felled trees onto structures and thoroughfares. Police report that at least two individuals in the Seattle, Washington, area have died due to trees falling on them in distinct events. A woman died while showering at her residence, and another fatality occurred in a homeless encampment. Forecasters have identified the event as a “bomb cyclone,” a phenomenon triggered by a rapid decrease in air pressure off the coast, leading to the swift intensification of the weather system. The South County Fire Department stated in a social media post that one woman died when a tree struck a homeless encampment in Lynwood, situated north of Seattle. The Bellevue Fire Department reported that another woman was killed in Kirkland when a tree fell onto her home as she was showering. Authorities indicated that after reaching the scene and verifying the woman’s death, “weather conditions were so dangerous in the vicinity” that they had to move the victim’s husband to a secure area. Additionally, two other individuals sustained injuries in Maple Valley, south of Seattle, when a tree fell onto their trailer home. During the storm, Washington’s Bellevue Fire Department posted on social media, stating, “It’s severe out there. Trees are coming down all over the city, with multiple falling onto homes.” The department advised, “If you are able, head to the lowest floor you can and stay away from windows. Do not go outside if you can avoid it.” Poweroutage.us reported that on Wednesday morning, over 700,000 residences and commercial properties in Washington were without electricity. This figure decreased to approximately 500,000 later that day. In California, around 15,000 customers experienced power interruptions. Schools throughout Washington were closed on Wednesday. Streets were covered with pine needles, leaves, and other storm-related debris, while the sound of chainsaws was audible in Issaquah, a city known for its salmon hatchery in the foothills of the Cascade mountains. A man attempting to reach his sister’s residence in Issaquah, located near Seattle, informed BBC News on Wednesday that a nearby residential courtyard, strewn with fallen trees, appeared as though it had been struck by a bomb. The US Weather Prediction Center (WPC) indicated a high probability of excessive rainfall in northern California, issuing warnings for flash flooding and mudslides. The San Francisco Bay area is projected to receive as much as 8in (20cm) of rain. The storm’s influence has also extended into Canada, where strong winds are the main concern, with gusts reaching up to 100mph (160km/h) recorded off the coast of Vancouver Island. The British Columbia Hydro and Power Authority reported that approximately 140,000 customers in British Columbia were without electricity. BBC Weather presenter Stav Danaos stated that while damaging wind gusts were anticipated to diminish on Wednesday, blustery conditions would likely persist along the Pacific coast, stretching from San Francisco to Vancouver Island. Furthermore, continuous heavy rainfall is forecast for much of the coast throughout Thursday and Friday, as a fresh “atmospheric river” of Pacific moisture moves inland. In addition to wind, rain, and snow, the storm carries the potential for flash flooding, rock slides, debris flows, and significant mountain snow in elevated regions. The weather system has already generated blizzard conditions across the Cascade mountain range, which spans both the US and Canada. The substantial, wet snow accumulated on the Cascades and North Rockies is expected to begin thawing by the week’s end with the arrival of milder air. This melting snow, coupled with additional heavy rainfall, is poised to cause severe flooding in areas from Northern California to Oregon, presenting a considerable risk of landslides as the week concludes. Meteorologists define a “bomb cyclone” as a storm that undergoes rapid intensification, characterized by a drop in its central air pressure of at least 24 millibars within a 24-hour period. These storms are termed “bomb cyclones” because of the explosive force generated by this swift pressure decrease. Such a storm encompasses a variety of weather phenomena, including blizzards, severe thunderstorms, and heavy precipitation. Such weather occurrences are not uncommon for this season. Comparable “atmospheric river” events—where localized bands of moisture move beyond tropical zones—have been observed across North America in recent weeks. However, the confluence of an atmospheric river and a bomb cyclone has the potential to produce a significant weather event.