'Bomb cyclone' strikes: 2 dead, widespread power outages in Washington

Editor's Note: This page is a summary of news on the Northwest bomb cyclone for Wednesday, Nov. 20. For the latest news, see our story for Thursday, Nov. 21.

Two people are dead and others injured as a "bomb cyclone" battered the Pacific Northwest with high winds and rain Wednesday, cutting power to hundreds of thousands in Washington state amid forecasts calling for more dangerous rain, flooding and snow in the region.

Two women in the Seattle suburbs were killed separately by falling trees, and two other people were injured by falling trees southeast of the city.

The ferocious storm is akin to a winter hurricane, with wind gusts of up to 70 mph, and it brings a slew of dangers. Besides downing trees and causing widespread power outages, the high winds have blocked roadways and smashed homes.

Following the bomb cyclone, the region faces days of rain, "life-threatening flooding'' and snow at higher elevations from another Pacific storm, the National Weather Service said Wednesday. That's part of an "atmospheric river" that could bring up to 16 inches of rain to areas of Northern California and southwest Oregon, the service said. Rock slides and debris flows are also probable.

Impacts of the first storm are expected to last through early Thursday, and the ensuing break will be short as the second system figures to peak Thursday night, the NWS said.

That second wave will carry even heavier rainfall that will turn into wet snow at the higher elevations of the Cascade Mountains, according to the weather service. That snowfall combined with wind gusts in the 60-mph range will lead to blizzard conditions.

Seattle has largest blackout since 2006

Though the majority of blackouts in Washington took place outside Seattle, the city endured its largest number of outages since 2006, the Seattle Times reported.

At one point Tuesday night there were 114,000 customers of the Seattle City Light utility in the dark, but that figure had dwindled to 36,000 by Wednesday at 1 p.m. PT.

"Restoring power to the remaining customers will depend on the severity of the damage," mayoral spokesperson Callie Craighead told the newspaper.

Besides blocking numerous roads and snarling traffic, the downed trees impacted mass transit in at least one other way. A large tree fell on a King County Metro bus Tuesday night in north Seattle, the Times said. No injuries were reported.

Tracy Meloy of Issaquah, about 17 miles southeast of Seattle, told the Associated Press she heard lots of noise from wind and debris throughout the night. When surveying the damage Wednesday morning, she noticed tree limbs and other vegetation on the road in front of her house.

“It looks like a forest floor instead of a street,” she said.

High winds and downed trees: A dangerous combination

Strong winds are knocking down trees across Washington, including in Lynnwood, where a woman in her 50s died after a large tree fell on a homeless encampment, South County Fire said Tuesday.

Washington power outage map: Bomb cyclone knocks out power to nearly 600,000 homes, businesses

Two other people were injured when a tree fell on a trailer less than 40 miles away in Maple Valley, firefighters in Puget Sound said on the X platform. One person was extricated quickly, but it took firefighters an hour to rescue the second, Puget Sound Fire said.

The fire department in Bellevue said trees were down all over the city and some were falling onto homes. The department warned residents to seek shelter on their lowest floor and stay away from windows.

In Seattle, fallen trees blocked roadways and trapped one person inside a vehicle, the fire department said.

More than 350,000 customers in Washington and 32,000 in California were out of power by 4 p.m. PT Wednesday, according to poweroutage.us. The outages, downed trees and high winds prompted at least one school district in Washington to cancel classes.

More: Bomb cyclones are powerful winter storms. Here's a visual breakdown of how they're created.

101 mph wind gust reported

The National Weather Service warned the wind gusts will likely increase the number of downed trees and power outages, particularly in coastal areas where heavy, wet snow has accumulated. Peak wind gusts of 101 mph were recorded in Canadian waters by a buoy off the coast of Vancouver Island, the National Weather Service in Seattle said.

Gusts reached 59 mph at Seattle-Tacoma International Airport on Tuesday night, and gusts of 53 mph were recorded in Eugene, Oregon.

Winds are expected to gradually decline by midday Wednesday with the departure from the region of the very deep low-pressure system brewing 300 miles off the coast of Washington that is responsible for them, the weather service said.

Seattle residents stay home, prepare for power outages

Austin Miller bikes to his retail job in downtown Seattle most days but chose to ride the bus Wednesday morning as heavy rain was falling. Miller, 30, said he’s taking his portable phone charger everywhere this week in case the power goes out.

On Tuesday night, Miller went straight home after work and stayed in, watching the new "Dune" television series on HBO to avoid the storm. The wind howled outside and the lights began to flicker around 8 p.m., Miller told USA TODAY. As the night wore on, sirens blared constantly outside the fire station across from his home in the city’s International District.

“They have an American flag out front, and I’ve seen that flag whip around pretty good,” Miller said, describing the wind.

Atmospheric river incoming

While the bomb cyclone moves away, prolonged heavy rain from an atmospheric river will bring more than a foot of rain to Northern California and southwest Oregon through Friday, the weather service said. A separate low-pressure system is forecast to strengthen off the Northwest coast Friday, bringing another round of high winds, amplifying the effects of the atmospheric river and exacerbating the risk of flooding.

Sometimes called "rivers in the sky," atmospheric rivers are a major factor in extreme rain and snowfall in the West. They function much like rivers on the surface but can carry considerably more water than the Mississippi River.

Snow levels in the mountains will rise rapidly Wednesday, and travel will be impossible at the pass level due to blizzard conditions in the Cascades and far Northern California.

AccuWeather warned Tuesday that the bomb cyclone would "act like a massive firehose of rain at low elevations and a giant snow gun over the high country."

"The storm is just beginning," said Rich Otto, a meteorologist with the NWS Weather Prediction Center in College Park, Maryland.

"The biggest surge is Thursday. We're looking at 10-15 inches of rain by Friday; some places, 20-inches," Otto said, with the main concerns for southwest Oregon and Northern California.

More: Washington power outage map: Bomb cyclone knocks out power to nearly 600,000 homes, businesses

What is a bomb cyclone?

A bomb cyclone – a potent cold-season coastal storm that's so-named due to its explosive strength – is colloquially known as a winter hurricane.

Such storms undergo an intensification process known as bombogenesis, which is a quick drop in atmospheric pressure, marking the strengthening of the storm, according to the National Oceanic and Atmospheric Administration.

Bombogenesis is said to occur when a storm's central barometric pressure drops at least 24 millibars in 24 hours. A millibar is a way of measuring pressure. The lower the pressure, the more powerful the storm.

Some of the most intense winter storms to batter the country's coasts have been bomb cyclones.

The word "bombogenesis" is a combination of "cyclogenesis," which describes the formation of a cyclone or storm, and "bomb" for its explosiveness.

"This can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters," NOAA said. "The formation of this rapidly strengthening weather system is a process called bombogenesis, which creates what is known as a bomb cyclone."

A record strong storm

Weather.com meteorologist Chris Dolce said in an online report the current storm "more than doubled'' the bombogenesis criteria: the barometric pressure dropping by 24 millibars or more in 24 hours or less.

In addition, Dolce reported that its estimated pressure dropped as low as 942 millibars, according to a Tuesday night analysis from NOAA's Weather Prediction Center. "That's pretty much on par with an October 2021 storm (942.5 millibars) for the lowest pressure in about 50 years of records for the northeast Pacific region."

(This story has been updated to add new information.)

Contributing: Claire Thornton, USA TODAY; Reuters

This article originally appeared on USA TODAY: 'Bomb cyclone' forecast says wind, rain and snow amid power outages