An enormous atmospheric river-fueled storm unleashed rain and furious winds across California on Sunday, leaving destruction and hazards in its wake.
Howling winds tore down power lines and trees, and scattered debris in communities across the state, prompting officials to issue the first-ever hurricane-force wind warning along the coast. By late afternoon, streets in both northern and southern regions of California were left submerged, with far more rain on the way.
Roughly 36 million people were under flood watches on Sunday evening as large metro areas, including the city of Los Angeles – where the star-studded Grammy awards were being held – braced for impact.
The storm also pummeled mountain communities with snow and whipped up steep waves along the coast. By 6pm, nearly 850,000 homes and businesses were without power, mostly concentrated along the coast and in snow-inundated districts at the center of the state.
The National Weather Service warned continuous rainfall would hit over a 48-hour period in some already sodden areas across the state, including the central coast, the Los Angeles basin and in the mountain ranges.
“This is a DANGEROUS SYSTEM [sic] with major risks to life and property,” NWS Los Angeles warned in a Sunday afternoon forecast discussion, adding that roads and highways would become inaccessible, rockslides were likely through canyons, and rising waters would surge into homes and businesses in low-lying neighborhoods.
Five rivers or creeks across the state had already exceeded flood stage on Sunday according to monitors with the National Oceanic and Atmospheric Administration, with more than a dozen more on watch.
Even though the extreme weather wreaked havoc in the northern part of the state, southern California will probably be hit even harder. The storm is expected to stall out over Santa Barbara, Ventura and Los Angeles counties. The dangerous deluge could dump up to 15in of rain in the foothills and mountains, and up to 6in in coastal areas and valleys.
Governor Gavin Newsom proclaimed a state of emergency in eight southern California counties as the storm swirled in Sunday afternoon and state and local agencies pre-positioned essential resources, including millions of sandbags, water rescue teams and high-water vehicles before the onslaught.
Most Los Angeles public schools are planning to remain open on Monday, unless conditions worsen, the superintendent Alberto Carvalho announced on Sunday. Cal State Fullerton and Cal State LA, two local universities, opted to hold classes virtually. Santa Barbara Unified school district announced its schools and offices would be closed Monday.
Wind gusts of up to 85mph were reported along the Big Sur coast on Sunday morning, as the storm pulled down power lines and created other hazards along Highway 1.
Communities tucked into mountain slopes, near surging rivers, or close to wildfire burn scars were put under mandatory evacuations or evacuation warnings, including in Ojai, Los Angeles and Santa Barbara. Water managers began releasing water from reservoirs that were nearing capacity in the central valley and Sacramento valley, Karla Nemeth, the director of the California department of water resources, said.
The deluge comes as communities across the state are still reeling from last week’s storm, which unleashed torrents and thunderstorms on Wednesday and Thursday and tested the capacity of infrastructure.
With the grounds saturated from the first storm, the NWS warned that dangerous flash flooding would occur more quickly.
Link to first-ever "Hurricane Force Wind Warning" issued by San Francisco Bay Area National Weather Service Forecast Office.https://t.co/2ZryeoFqXg
— Kevin Dayton (@DaytonPubPolicy) February 4, 2024
From westernmost point of Monterey Peninsula down Big Sur coast to area where Hearst Castle is located. pic.twitter.com/tRIpufs5NP
California could have several more wet weeks ahead, said climate scientist Daniel Swain during a discussion of the system posted on YouTube on Friday. During strong El Niño years the wet season typically peaks between February and March, he noted. “There are at least 6-7 more weeks of potential [for storms] and I would not be surprised if there was another major storm cycle at some point in that window.”
What is an atmospheric river? And other weather terms explained
Here's a short breakdown of the different kinds of storms that have lashed the west coast of North America this winter.
Atmospheric river
The National Oceanic and Atmospheric Administration refers to these as “rivers in the sky” for good reason. Characterized by long streams of moisture in the atmosphere, the average atmospheric river carries an amount of water vapor that rivals the flow at the mouth of the mighty Mississippi River – and strong ones can hold up to 15 times that amount. That moisture is released as rain or snow when ARs make landfall and typically are accompanied by strong, gusty winds adding to their destructive tendencies.
Pineapple express
These particularly strong atmospheric rivers are named for their origin. Pulling moisture from the Pacific around Hawaii, Pineapple Express storms have been known to unleash torrents of precipitation when they reach the west coast of the US and Canada – and have dumped roughly 5in of rain on California in a single day, according to the National Ocean Service.
Bomb cyclone
These low-pressure storm systems help create atmospheric rivers, pushing them from the Pacific to the coast. Unlike hurricanes or other storms where the center is the strongest, bomb cyclones can generate the worst weather at their edges.
El Niño
This is a climate pattern characterized by unusually warm surface ocean temperatures in the tropical Pacific. Along with its counterpart La Niña – which, in turn, refers to a period of colder-than-average sea surface temperatures – these patterns can impact weather around the world. While the weather doesn’t always align, El Niño is associated with warmer temperatures, and generally delivers drier conditions in the northern US and Canada, and wetter ones – bringing increased flood risks – through the south.
– Gabrielle Canon, US climate and extreme weather correspondent
El Niño, a climate pattern associated with increased ocean temperatures in the tropical Pacific, can supercharge atmospheric rivers like the ones now creating strong storms over California with vapor that evaporates off the warmer surface waters. While there can be variability, El Niño typically delivers hotter, wet winters in California and other parts of the US south-west.
Meanwhile, California reservoirs already stood at 115% of average going into this system, according to the California department of water resources, and water managers in the central valley opted to release waters ahead of the storm to ensure they wouldn’t spill over. With weeks left to go in California’s wet season, and exceedingly wet conditions still in the forecast, several regions across the state had already exceeded or were nearing average precipitation levels.
Scientists have warned that this is a taste of what’s to come as the world warms, when wetter conditions with smaller snowpacks are expected to become the norm. “This tells us something about what California winters may look like increasingly in a warmer climate,” Swain said, noting that it’s both an El Niño story and a climate crisis story.
