California weather: ‘Pineapple Express’ slams west coast with heavy rain and win

The first of two back-to-back atmospheric rivers drenched Northern California on Thursday, flooding roads while triggering statewide storm preparations and calls for people to get ready for powerful downpours, heavy snow and damaging winds.

Heavy rain and gusty winds that began hitting the San Francisco Bay Area on Wednesday evening were expected to continue powering down the coast, according to the National Weather Service.

The river of rain “will be taking aim at mostly Southern California” on Thursday, weather service forecaster Bob Oravec said.

The Los Angeles and San Diego areas will be in the bullseye for heavy rain on Thursday, “especially for some of the higher elevations where they tend to get most of the rainfall — or the heaviest rainfall — with these atmospheric river events,” he said.

The weather service issued a flood watch into Friday morning for the Bay Area and the Central Coast because of possible flooding of rivers, streams, some roads and areas scarred by previous wildfires.

Forecasters also said the Central Coast could see waves up to 18 feet high on Thursday and Friday.

Service on San Francisco’s iconic cable cars were halted as a safety precaution, and Pacifica, a coastal city in San Mateo County, saw more than an inch of rain in a single hour.

A massive atmospheric river known as a “Pineapple Express” is barrelling towards the US West Coast, with torrential rain and powerful winds raising the threat of heavy flooding and landslides.

Forecasters warned that up to eight inches of rain expeced in some areas of northern California.

Here’s what you need to know about the approaching storms:

According to the National Oceanic and Atmospheric Adminstration (NOAA), atmospheric rivers are narrow regions in the atmosphere that transport much of the moisture from the tropics to northern latitudes. The weather systems are part of the Earth’s ocean water cycle, and are tied closely to both water supply and flood risks.

A well-known example of a strong atmospheric river is called the “Pineapple Express” – predicted to soon hit California – because moisture builds up in the tropical Pacific around Hawaii and can wallop the U.S. and Canada’s West Coasts with heavy rainfall and snow.

Prevailing winds cross over warm bands of tropical water vapor to form a “river,” which travels across the Pacific as part of the global conveyor belt. When it reaches the west coast, the Pineapple Express can dump as much as five inches of rain on California in one day.

According to NOAA, atmospheric rivers come in all shapes and sizes, but those that contain the largest amounts of water vapor and the strongest winds are responsible for extreme rainfall and subsequent flooding. These events can affect the entire west coast of North America, often disrupting travel and damaging property in the process.

The Los Angeles branch of the National Weather Service issued a seven-day summary of the appraoching storms, advising residents to begin preparing.

The forecaster said that the first storm – a “Pineapple Express” lasting Wednesday and Thursday – would see moderate flooding focused on roads.

A more severe second storm, taking place from Sunday to Tuesday or Wednesday next week, would see growing potential for damaging flooding rain, strong winds, and lots of mountain snow.

“Start preparing now. Adjust plans. Grab sandbags. Mountain communities, grab extra supplies in case you are stranded,” NWS LA wrote on X.

The “Pineapple Express” storms and subsequent weather warnings come after the city of San Diego in southern California recovers from life-threatening floods.

Last week, San Diego Mayor Todd Gloria declared a state of emergency after torrential rain deluged the area, causing flash flooding which inundated people’s homes and cars.

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Earlier on Wednesday, the California Governor’s Office of Emergency Services activated its operations center and positioned personnel and equipment in areas most at risk from the weather as the first of two atmospheric river storms hit the state.

Brian Ferguson, California OES deputy director of crisis communications, characterized the situation as “a significant threat to the safety of Californians” with concerns for impact over 10 to 14 days from the Oregon line to San Diego and from the coast up into the mountains.

“This really is a broad sweep of California that’s going to see threats over the coming week,” Mr Ferguson said.

John Feerick, senior meteorologist for AccuWeather.com said that the “Pineapple Express” storm – the first of two atmospheric river storms – would gradually work its way southeastward across across California over the next 24 hours.

“It will just kind of gradually pushout eastward into central California and places like Fresno and Bakersfield late this afternoon or this evening, and then it’ll move into Los Angeles by late tonight,” he said, speaking to The Independent.

“Then the heaviest rain tomorrow is going to be from Los Angeles eastward and southeast or through San Diego and over to Palm Springs. That’s where we’ll see the heavy rain kind of sort of the day tomorrow.

“So yeah, it’s just kind of gradually works southeastward across across the state the next 24 hours.”

Commuters in the Los Angeles should consider working from home if possible or exercise caution on roads as heavy rain storms close in.

Experts have advised those who are travelling, should do so only if necessary and allow extra time to reach destinations. If encountering high water, alternate routes should be sought.

On Wednesday night or Thursday morning, people should consider working remotely as widespread highway flooding is expected in the Los Angeles area.

Officials have urged precaution as the first of the two imminent atmospheric river storms hits California.

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