An atmospheric river, known as a “Pineapple Express,” is set to bring significant rainfall to parts of California next week, with meteorologists warning that flooding may be possible.
Atmospheric rivers vary in size and intensity, but those with the highest water vapor content and strongest winds can bring extreme rainfall and flooding, according to the National Oceanic and Atmospheric Administration (NOAA).
The NOAA explains that atmospheric rivers are long, narrow bands in the atmosphere that transport large amounts of water vapor from the tropics. Their size and strength can vary significantly, but on average they carry a volume comparable to the flow of the Mississippi River at its mouth. Exceptionally strong atmospheric rivers can transport up to 15 times that amount. When they make landfall, they typically release this moisture as rain or snow and can often cover a huge region moving into a coastal area.
AccuWeather meteorologist Matt Rinde told Newsweek that “Pineapple Express” refers to an atmospheric river originating in the tropical Pacific, typically near Hawaii. “This carries a considerable amount of liquid that gets ‘squeezed out’ as it reaches land,” Rinde said. These typically form alongside large storm systems in the upper atmosphere. They are fairly common from a few to several times a year, said Rinde. A forecast map from AccuWeather, shared with Newsweek, showed that parts of Northern California were expected to see heavy rain and snow Friday night through Monday.
Rounds of intense rainfall, as well as landslides, road closures, and travel delays were also possible, it said. A separate forecast map showed that as much as 8-12 inches of rainfall was expected in areas north of Santa Rosa.
AccuWeather meteorologist Matt Rinde told Newsweek: “Since there is no hard and fast definition, some events may or may not be attributed to an atmospheric river. We tend to move toward calling it that in order to convey impacts related to the coming event.”
Meteorologist Cory Kowitz said on X, formerly Twitter: “The atmospheric river is gonna be flowing big-time over the next week. In Northern Cal, rainfall could reach 20″+ in spots. In the Sierra Nevadas, 100″+ of snowfall is possible.”
NWS Weather Prediction Center said on X: “Impressive rainfall totals will accompany a multi-day atmospheric river event across Northern California and southern Oregon with flooding impacts possible.”
Rinde told Newsweek that the event is expected to last through at least Tuesday, primarily affecting Northern California. However, it may also impact parts of Washington and Oregon, though to a lesser degree.
ALSO READ: Pentagon Halts Policy Supporting Troops’ Access To Abortions
