Historic “Pineapple Express” Delivers Record-Breaking Rainfall and Flooding to Los Angeles County
Los Angeles County recently endured an unprecedented weather event, experiencing its wettest Christmas period in recorded history. A potent atmospheric river, colloquially known as a “Pineapple Express,” unleashed torrential rainfall from December 22nd through December 29th, shattering long-standing records, triggering widespread emergency declarations, and impacting communities across the region. This wasn’t simply a heavy rain; it was a historically critically important meteorological event with considerable consequences.
Unprecedented Rainfall Totals and Record-Breaking Statistics
The sheer volume of precipitation was remarkable. Downtown Los Angeles accumulated approximately 4 inches of rain between Christmas Eve and December 26th – the second-highest total for that period since 1889. Santa Monica recorded 3.1 inches at the Santa Monica Airport (SMO), while localized measurements in North of Montana (NOMA) reached 4.8 inches. However, the most dramatic rainfall totals where observed in the mountainous areas. Mount Wilson, nestled within the San Gabriel Mountains, registered over 8 inches during the five-day storm, with some higher elevation areas receiving nearly 18 inches throughout the week.
Airports also bore witness to the storm’s intensity. Los Angeles International Airport (LAX) surpassed a 1971 record with 1.88 inches of rain on Christmas Eve. Burbank Airport recorded 3.42 inches, establishing a new daily high. Further north, Santa Barbara Airport experienced its wettest Christmas on record, measuring 5.91 inches on Christmas Day. Meteorologists place this event among the top five to ten wettest starts to Southern California’s winter rainy season, highlighting its extraordinary nature.
Widespread Flooding, mudslides, and Emergency Responses
The extreme rainfall quickly overwhelmed drainage systems, leading to widespread flooding and dangerous mudslides throughout Los Angeles County. Major transportation arteries, including Interstate 5 in Sun Valley, were forced to close due to inundated lanes. Numerous street intersections, from eagle Rock to South Los Angeles, became impassable, trapping vehicles and disrupting daily life.
Emergency responders were stretched thin. The Los Angeles Fire Department (LAFD) executed at least three swift-water rescues by christmas Eve, including a harrowing incident where a woman was rescued after being swept nine miles downstream by the powerful currents of San Jose Creek. Authorities repeatedly urged residents to avoid travel and remain vigilant as crews worked to address flooded streets, downed power lines, and escalating debris flows.
Hillside communities were particularly vulnerable to mudslides. The mountain town of Wrightwood was hit hard, with torrents of mud surging through homes, trapping residents and vehicles. San Bernardino County fire officials issued shelter-in-place orders due to impassable,mud-covered roads.Mandatory evacuation orders were implemented for areas within the Santa Monica Mountains prone to mudslides, specifically targeting Pacific Palisades and Malibu, regions still recovering from previous wildfires.
Government Response and Infrastructure Impact
Recognizing the severity of the situation, Los Angeles Mayor Karen Bass declared a local state of emergency, and Governor Gavin Newsom issued an emergency proclamation to facilitate the mobilization of state resources. By Christmas Day, city agencies had responded to over 350 traffic collisions and more than 600 reports of downed trees. Approximately 4,000 customers of the Los Angeles Department of Water and Power (LADWP) experienced power outages, though crews swiftly restored service to all but two traffic signals by Christmas night.
Adding to the unusual nature of the storm, a small EF-0 tornado with 80 mph winds touched down in Boyle Heights on christmas morning, causing damage to roofs and a strip mall. While the storm system was linked to at least four fatalities statewide, Los Angeles County fortunately reported no direct storm-related deaths.
Significant infrastructure challenges remain. Caltrans reopened a 3.6-mile stretch of Topanga Canyon boulevard on Saturday, December 30th, after extensive debris removal. However, the corridor remains an active work zone related to ongoing Palisades Fire recovery efforts and is subject to nightly closures from midnight to 5 a.m.
Public Health Concerns and Beach Closures
The heavy rainfall also triggered public health concerns. County health officials issued warnings regarding ocean water quality, advising beachgoers to avoid all water contact, particularly near storm drains, creeks, and rivers. The storm runoff carries contaminants, debris, and trash, leading to potentially elevated bacteria levels and posing a health risk.
Looking Ahead: Understanding Atmospheric Rivers and Future Preparedness
This recent event underscores the increasing frequency and intensity of extreme weather events linked to climate change.Atmospheric rivers, like the ”Pineapple Express,” are long, narrow bands of concentrated moisture in the atmosphere. While they are a natural part of California’s climate and crucial for replenishing water supplies, their increasing intensity poses significant risks.
Understanding the dynamics of these storms and investing in robust
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