After rapid intensification of a historically intense bomb cyclone off the Pacific Northwest coast, damaging wind gusts and power outages struck the Seattle region, killing at least two people — and the storm’s onslaught is just getting started. Attention is now shifting to a powerful atmospheric river battering the West Coast.
The atmospheric river — a thin band of copious tropical moisture — will unleash its fire hose while crawling along. Day after day of heavy precipitation threatens to produce life-threatening flooding. The heaviest rain is expected between Eureka, California, and the San Francisco Bay Area, and a large portion of Northern California into southwestern Oregon could experience 6 to 12 inches of rain. Some spots could pick up 12 to 18 inches or more.
Flood watches are in effect from the north bay to the state border, with a flood warning for far-southwest Oregon, until Friday night. As much as six inches has fallen already in the area under advisory. As soils fully saturate farther south, flooding risks will notably increase into Wednesday night.
Winter storm warnings remain in effect for the mountains of northern into central California. Highlighting the dynamic nature of the storm, red-flag warnings for high wind and fire spread are in effect east of the Sierra Nevada. High surf is also ongoing on the coast around San Francisco, where wave heights of 15 to 20 feet are possible on exposed beaches.
The bomb cyclone rotating off the Pacific coast sent howling winds barreling across the Northwest on Tuesday evening that flattened trees, blocked roads, downed utility lines and left more than half a million people without power. Two women — one who was in her shower in a wooded community east of Seattle, and a second in a homeless encampment north of the city — were killed by falling trees during the storm, authorities said.
The unusually powerful winds gusted up to 59 mph at SeaTac Airport and up into the 70s at higher elevations in the Cascade mountains. Gusts of 60 to 65 mph were reported in many locations near the coast or just inland across western Washington, Oregon and into Northern California.
As trees and power lines started to crash down, firefighters in the region were inundated with phone calls seeking help. Firefighters in Bellevue, a city of some 150,000 people east of Seattle, received more than 200 calls over an eight-hour period, said Heather Wong, a fire department spokeswoman, including from people trapped in elevators and in their cars.
A tree crashed through one residence in Bellevue’s Bridle Trails neighborhood, a wooded enclave known for its equestrian facilities, just before 7 p.m. The husband at the home reported that his wife was trapped in the shower; when fire fighters arrived, they determined that the woman, who was in her 60s, had died, Wong said.
The husband was taken to safety because the wind was still blowing “incredibly,” Wong said. “It was too dangerous for anybody to be there,” she said.
Around the same time, a large tree fell on a homeless encampment in Lynnwood, a city north of Seattle, according to a statement from the South County Fire Department.
“Tragically, a woman in her 50s died,” the statement said.
As of Wednesday evening, there were still widespread power outages across Washington state and additional outages in California.
The storm also snarled transportation: Heavy snow forced the closure of Interstate 5 in California between parts of Shasta and Siskiyou counties near the Oregon border. All vehicles, except four-wheel-drive vehicles with a full set of snow tires, were required to use chains on a stretch of the highway that spanned the state line, officials said.
The weather also caused hundreds of flight delays and dozens of cancellations at San Francisco International Airport, according to the tracking site FlightAware.
The storm’s remarkable development
On Tuesday evening, a storm-fueling bomb cyclone strengthened to at least 942 millibars, unleashing strong winds, heavy rain and blizzard conditions in the mountains. Winds near its center reached hurricane force, with reported gusts over 100 mph.
As impacts intensify from the Level 4 of 5 atmospheric river, soils are becoming increasingly saturated, leading to rising waters. “Significant flood risks will continue to increase [Thursday] along with rock and land slides,” wrote the National Weather Service’s Weather Prediction Center. In the zone with heaviest expected rain, the Weather Service is expecting a Level 3 of 4 risk for excessive rainfall Wednesday, a rare Level 4 risk Thursday and another Level 3 risk Friday.
As the bomb cyclone rapidly reached peak intensity late Tuesday, it battered parts of the Pacific Northwest with damaging wind gusts. The gusts were fueled by rapid strengthening of the low-pressure system, with the storm’s central pressure dropping from about 1,000 millibars to 942 millibars over 24 hours, easily doubling the 24-millibar drop in 24 hours that characterizes a bomb cyclone.
Serious rainfall ahead with the storm’s slow movement
The atmospheric river is intense, has the potential for heavy precipitation and will be long-lasting because of a stalled weather pattern. It’s a potentially fateful matchup for the region that will be hit hardest.
Occasionally moderate rain arrived in Northern California overnight and fell steadily Wednesday. Eureka on the northwest coast picked up more than an inch through midday. Rain was intensifying in parts of the region, a trend to continue into the night. Crescent City reported heavy rain and lowered visibility near the Oregon border.
Rainfall rates into Wednesday night could temporarily approach an inch per hour, while the wettest spots are expected to average about 2 to 3 inches every six hours.
Heading into Thursday, the fire hose of moisture is forecast to ramp up further when as much as 3 or 4 inches could fall during consecutive six-hour stretches.
The initial bomb cyclone should slowly weaken as it approaches the British Columbia coastline through Thursday, but it may regenerate into Friday, renewing a coastal wind threat and perhaps enhancing precipitation.
The highest rain totals are expected to fall between the northern portion of the Bay Area to around the California and Oregon border region, where a wide swath with rainfall of 6 to 12 inches is likely. Coastal and inland ranges are likely targets for the most significant totals overall. Some mountainous locations too warm for snow could see 20 inches of rain.
Five to 10-plus feet of snow could accumulate in the Klamath Mountains of California. Mount Shasta is forecast to see more than 100 inches fall through Saturday amid whiteout conditions.
Storm conditions will linger into next week
A stalled weather pattern could mean the storminess lingers a while along the West Coast.
The large gyrating dip in the jet stream off the Pacific Northwest is predicted to sit and spin into the weekend and perhaps into the subsequent days.
And the bomb cyclone isn’t the only unusually powerful dip in the jet stream across the North American region.
Why doesn’t this storm have a name?
Although the bomb cyclone reached historic power, developed hurricane-force winds, battered the Pacific Northwest and is now set to help deliver days of flooding, it does not have an official name.
In Europe, winter storms are named by more than one meteorological agency, with cooperation among many of them. And, of course, hurricanes and tropical storms get names.
But the Weather Service does not name winter storms.
There’s been debate in the United States over whether to name big storms outside hurricane season, though no consensus has been reached.
