This week in California, the Pineapple Express is set to bring over 8 inches of rain to some coastal ranges, potentially leading to significant flooding in Los Angeles and San Diego. The Pineapple Express, an atmospheric river originating near Hawaii, funnels an immense amount of moisture towards the West Coast, carrying up to 27 times the water volume of the Mississippi River, equivalent to 10-15 inches of rain.
“What we’ve got going now is a very active period when the the upper-level jet is stretching across the Pacific,” Marty Ralph, director of the Center for Western Weather and Water Extremes, told FOX Weather on Monday. “There’s a lot of moisture being transported in a series of atmospheric river storms associated with that. And they’re sort of stalled a bit over the Northwest for a few days here. And soon they’re going to move down the coast along into California.”
Meteorologist Bob Van Dillen outlines a dire scenario: “That jet stream is going to be oriented right from west to east, and that means very warm air and a lot of Pacific juice coming right across parts of California into northern New Mexico.” This warm, moisture-laden system is not only poised to deluge coastal regions but also to spike river levels, elevate landslide risks, and deposit immense quantities of snow in the Sierra Nevada.
“Very few ensemble members are showing AR (atmospheric river) 5. Numbers are showing here for the majority are showing AR 3 right now in the Northwest, and then getting into Central California/Northern California, AR 3 conditions look to be most likely. And Southern California could even get AR 1,” explained Ralph.
The National Weather Service (NWS) in Seattle warns of possible record warmth through Tuesday, underscoring the tropical nature of the system and its ability to carry prodigious amounts of precipitation rapidly across the Pacific. The Bay Area and northern California are primed for 3 to 8 inches of rain. “The good news here is it’s going to be strong, it’s going to be heavy at times, but it’s going to be transient, it’s going to be moving pretty quickly,” Van Dillen said.
Experts at the Climate Prediction Center have already indicated a moderate risk for heavy precipitation, heavy snow, and high winds for regions in the Western US, with potential flooding along the California coast and in Arizona from Feb 2 through Feb 5. “Snow, it’s coming in and that could be pretty decent for higher elevations, Sierra Nevada range all the way through the four corners and northern Nevada,” Van Dillen said.
Flash flooding is likely north of the San Francisco Bay Area, where the heaviest rain is forecast to fall.
“Shallow soils on steep hillslopes are approaching saturation,” wrote the San Francisco NWS office in an advisory. “This coupled with the forecasted precipitation means widespread shallow landslides are likely.”
Amy Freeze, a FOX Weather meteorologist, emphasizes the gravity of the situation: “This has got all the hallmarks of a high-end flooding situation for California, some beach erosion, mudslides, potentially, and a lot of mountain snow.” With soils nearing saturation from prior storms, the influx of rain will rapidly flow into creeks, rivers, and urban streets, elevating the risk of flooding and infrastructure damage.
Relevant articles:
– Pineapple Express headed for California as flooding, wind, snow expected
– “Pineapple Express” atmospheric river could bring heavy rain to Northern California next week, CBS San Francisco, Wed, 24 Jan 2024 23:18:00 GMT
– Two more atmospheric rivers take aim at California, Northwest bringing flood threat, Fox Weather, Sun, 28 Jan 2024 13:17:00 GMT
– How rising temperatures are intensifying California’s atmospheric rivers, Grist, Wed, 15 Mar 2023 07:00:00 GMT