The first of two severe storms due to an atmospheric river drenched California on Thursday, bringing an intense downpour that flooded roads and toppled trees while officials warned residents to prepare for a “significant threat” as another storm looms over the weekend.
The fast-moving storm kicked off with heavy rain and gusty winds that hit the San Francisco Bay Area and then moved south, arriving in Los Angeles in time to snarl the Thursday morning commute and cause flooding.
Forecasters had warned that the river of rain would largely take aim at southern California on Thursday.
The Los Angeles and San Diego areas were in the bull’s-eye for heavy precipitation.
As sheets of rain fell in San Diego, Ruben Gomez cleaned debris from storm drains in his parents’ neighborhood, which was hit hard by flooding from a storm in January.
He piled sandbags around what was left of their home after the previous deluge. Firefighters had had to rescue his parents, both 82, after the home filled with water reaching 6ft (2 metres). His father spent two days in the hospital with hypothermia, and his mother spent a week there, after water entered one of her lungs.
“Every hole in the house, I’ve got plugged with plastic and paper to make sure water doesn’t go up so high again,” Gomez said.
On Thursday, southern Los Angeles county was hit hard by flash flooding. Vehicles plowed through water on low-lying sections of freeways and at least one underpass beneath a rail crossing in Long Beach was inundated, submerging a car.
Seal Beach, south of Los Angeles, saw flooding along the Pacific Coast highway, which temporarily closed parts of the freeway. An employee swept water out of a storefront in the city’s downtown as onlookers dodged puddles after the rain slowed around noon.
In nearby Costa Mesa, a rescue team pulled someone from a flowing storm channel. The person was taken to a hospital in stable condition, the Orange county fire authority said in a social media post. The fire authority also rescued a man who had been trapped on a small island in the Santa Ana riverbed, surrounded by rushing water. A paramedic had to be lowered by a helicopter to grab the man and whisk him to safety.
Quick Guide
What is an atmospheric river? And other weather terms explained
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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
Service on San Francisco’s cable cars was halted as a safety precaution, and Pacifica, a coastal city in San Mateo county, saw more than an inch (2.5cm) of rain in a single hour.
Widespread coastal flooding was reported on Wednesday in Humboldt county, said the weather service office in the northern California city of Eureka, which recorded a daily record with more than 2in of rainfall. Scattered power outages were reported.
The storms also brought heavy snowfall to areas of higher elevation, a promising sign for the state’s meager snowpack, which currently stands at just 52% of the annual average. The Mammoth Mountain ski resort in the Sierra Nevada reported 12-14ins (30-36cm) of snow overnight. Heavy snowfall was also reported in mountains east of Los Angeles.
The storm came a week after heavy rain caused flash flooding that inundated homes, caused the river to surge and overturned cars in the county. Hundreds of people had to be rescued as the waters rose.
The “Pineapple Express” – called that because its long plume of moisture stretched back across the Pacific to near Hawaii – will be followed by an even more powerful storm on Sunday, forecasters said.
Last winter, California was battered by numerous drought-busting atmospheric rivers that unleashed extensive flooding, big waves that hammered shoreline communities and extraordinary snowfall that crushed buildings. More than 20 people died in storms described as one of “the most deadly natural disasters in the modern history” of California.
The second storm headed to the state this week is already predicted to be “the largest storm of the season”, according to the National Weather Service. The worst part of the storm will hit late Sunday into Monday as it stalls over Point Conception in Santa Barbara county.
“This system will likely produce 24 to 36 hours (or more) of continuous rain,” the weather service wrote Thursday.
Models suggest it could intensify as it approaches the coast of California, a process called “bombogenesis” in which a spinning low-pressure system rapidly deepens, Swain said in an online briefing on Tuesday. The process is popularly called a bomb cyclone.
That scenario would create the potential for a major windstorm for the San Francisco Bay Area and other parts of northern California as well as heavy rain, said Daniel Swain, a climate scientist at the University of California, Los Angeles.
Gabrielle Canon contributed reporting