California residents are preparing for the arrival of two atmospheric river storms, commonly known as a “Pineapple Express,” which are forecasted to bring heavy rain and upper-elevation mountain snow across the state over the next week.
What is a Pineapple Express?
According to the National Oceanic and Atmospheric Administration (NOAA), atmospheric rivers are narrow regions in the atmosphere that transport a significant amount of moisture from the tropics to higher latitudes.
When these moisture bands originate in the tropical Pacific Ocean near Hawaii and concentrate their energy on the West Coast of the United States, they are referred to as a Pineapple Express.
Starting on Wednesday and lasting for a week, California will experience two Pineapple Express storms, bringing substantial rainfall and strong winds. UCLA climate scientist Daniel Swain described these storms as “a true atmospheric river” and “a classic, moderate-to-strong atmospheric river.”
Timing of the two storms
Both storms will impact all major population centers in California. The first storm is expected to arrive in Northern California on Wednesday, potentially bringing 2 to 4 inches of rain in some areas, along with winds exceeding 30 miles per hour. While the first storm will primarily bring warm air, resulting in significant snowfall only in higher elevations, the second storm, anticipated to arrive on Sunday, will bring colder air and heavier snowfall to the Sierra Nevada mountains.
Storm No. 2 is forecasted to bring heavy rainfall and strong winds, with gusts reaching up to 70 miles per hour in Northern California. Southern California, in particular, faces the risk of very heavy rainfall, with the Los Angeles region potentially receiving up to 7 inches of rain before the storm passes next Wednesday.
Potential for flooding
Both storms carry the risk of flooding, with the first storm posing a threat to urban and small stream areas in Northern California. The second storm, intensified by a record-breaking low-pressure system, is of greater concern for Southern California, where the ground is already saturated from the previous rainfall.
Southern California could experience two to three times more rain than Northern California from the second storm, with the Los Angeles region bracing for significant rainfall from Sunday through Wednesday.
These atmospheric river storms underscore the importance of preparedness and vigilance among California residents in the face of extreme weather events.