A bomb cyclone barreled through California last week, spawning two rare tornadoes and pounding the state with flooding rain, intense wind and severe thunderstorms, the latest saga amid one of the stormiest seasons in recent history for the Golden State.
At least five fatalities are being blamed on the storm, including at least three due to powerful winds blowing trees over and landing on occupied vehicles, according to The Associated Press. Two of the deaths occurred in the town of Portola Valley, located in the Bay Area, and in Rossmoor, about 7 miles east of Long Beach in Southern California.
One man inside a tent died Tuesday night near Lake Merritt in Oakland, after a tree fell onto the tent. Two others died at Zuckerberg San Francisco General Hospital while receiving treatment for injuries, according to city officials, in separate storm-related incidents.
A San Francisco police sergeant was hospitalized Tuesday with life-threatening injuries after a tree struck the car he was driving during the afternoon, with firefighters responding to the scene and removing the sergeant from the vehicle. His updated condition is not known as of Wednesday afternoon.
A tornado was seen swirling over east of downtown Los Angeles in Montebello late Wednesday morning, with the AP reporting that one person was injured. The tornado damaged at least 17 buildings and even more vehicles, and forced buildings in the area to evacuate. The National Weather Service later confirmed the damage was consistent with an EF1 tornado, which is the strongest tornado to impact the Los Angeles metro area since March 1983.
The NWS also confirmed Wednesday that an EF0 strength tornado touched down in Carpinteria, 90 miles northwest of Los Angeles, on Tuesday with estimated winds up to 75 mph. The tornado hit a mobile home park, damaging about 25 homes.
Downed trees also contributed to nearly 250,000 power outages across the state on Tuesday afternoon, many of which were located in and south of the Bay Area. The number of households and businesses without service was halved by Wednesday afternoon, according to PowerOutage.us, although some of the outages were expected to linger for several days in the hardest-hit areas of California.
“The impacts from the event resembled that of a landfalling strong tropical storm – likely the closest San Francisco residents will ever come to experiencing that meteorological phenomenon,” AccuWeather Director of Forecast Operations Dan DePodwin said.
“Tropical storm-force wind gusts (39-73 mph) were reported for seven consecutive hours in Oakland,” he added. “Despite being vastly different in structure than a tropical system, the compact area of low pressure on radar resembled the eye of a hurricane as it moved onshore Tuesday afternoon just south of San Francisco.”
With the ground already saturated from the recent rounds of atmospheric rivers, the intense winds easily blew over large trees. Santa Cruz and the surrounding mountains experienced some of the worst of the storm with wind gusts well over 80 mph, shredding trees and snapping power lines. Mountain roads that were littered with debris were closed through Wednesday as emergency responders frantically worked to clean up in the wake of the powerful system.
“There are many historic examples of significant high-impact wind and rain events in the San Francisco Bay Area, perhaps the most notable being on Dec. 12, 1995,” DePodwin said.
As intense, wind-driven rain pelted Central California, thunderstorms rumbled over Southern California. The severe storms in the Los Angeles area Tuesday evening showered parts of the city with hail, a rare occurrence in the City of Angels.
Downtown Los Angeles measured 1.43 inches of rain on Tuesday, washing away the previous daily record for March 21, of 1.34 inches that was set more than a century ago in 1893. The 6.38 inches of rain that have fallen in the city this month has made it the wettest March on record since 1995 when 6.98 inches of rain was measured.
Farther inland, the combination of heavy rain and snowmelt transformed a farm field into a massive lake in Corcoran, about 45 miles south of Fresno.
As rain sparked flash flooding and mudslides in the lower elevations, snow piled up in the mountains.
Mammoth Mountain measured 18 inches of snow on Wednesday, sending the seasonal snowfall total to 664 inches — just 4 inches shy of the all-time record set during the winter of 2010-2011.
“We are stoked to announce that we will be open daily for skiing and riding until AT LEAST the end of July,” the resort stated in a Facebook post on Tuesday. “As always, we do not have a closing date set, but will plan to stay open as long as conditions allow. Sitting on one of the deepest base depths ever recorded at Main Lodge, it’s going to be some of the best spring skiing and riding we’ve ever seen.”
So much snow has accumulated in the mountains that the California National Guard has had to airlift hay and starving cattle that cannot eat grass that was trapped under deep snow.
AccuWeather forecasters say that the latest California storm fell just short of being considered an atmospheric river, but it was still a force to be reckoned with.
As the center of the system strengthened on its final approach to the California coast, it underwent a meteorological process known as bombogenesis, otherwise known as a bomb cyclone.
In most instances, a bomb cyclone is when the central pressure of the storm plummets by 0.71 of an inch of mercury (24 millibars) in 24 hours. However, the National Weather Service says that the benchmark is different depending on the latitude of the storm.
For the zone just south of the Bay Area, the central pressure of a storm only needs to drop 0.47 of an inch of mercury (16 mb) over a 24-hour period to be considered a bomb cyclone. This adjusted benchmark was achieved late Monday through Tuesday afternoon as the center of the storm rapidly intensified from 29.68 inches of mercury (1005 mb) to 29.08 inches of mercury (984 mb).
As Californians begin to clean up in the wake of the bomb cyclone, they will also begin to once again prepare for another round of snow, wind and rain.
“There will be no rest for the weary in California next week,” said AccuWeather Senior Meteorologist Heather Zehr. “Fortunately, the overall strength and amount of moisture in the next storm will be lower, and it seems Southern California, which was one of the hardest hit areas from the last storm, might be largely spared from the heaviest precipitation.”
Produced in association with AccuWeather