California State of Emergency The Science Behind the "Pineapple Express" Storm
- Governor Newsom has mobilized state resources to combat a massive atmospheric river dumping up to 14 inches of rain on Southern California.
- Recent wildfire zones are at critical risk of mudslides due to "hydrophobic soil" that cannot absorb the deluge.
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| Photo by Lala Miklós on Unsplash |
Southern California is currently besieged by a "once in five to 10 year" weather event, as a powerful atmospheric river known as the Pineapple Express channels deep tropical moisture directly from Hawaii into the coastal mountains. Governor Gavin Newsom has proclaimed a state of emergency for Los Angeles and surrounding counties, mobilizing swiftwater rescue teams and pre positioning fire engines to combat a storm that officials warn places "lives and property in great danger". The physics of this storm are particularly punishing a low pressure trough is driving the moisture perpendicular to the mountain ranges, maximizing rainfall rates to as high as 1.5 inches per hour, with total accumulation expected to reach a staggering 14 inches by Friday.
The most acute danger lies not just in the water volume, but in where it lands. Communities like Pacific Palisades and Altadena are facing a heightened threat due to "burn scars" areas recently devastated by wildfires where the soil has become hydrophobic. In these zones, the ground repels water like concrete rather than absorbing it, creating ideal conditions for sudden, catastrophic mudslides and debris flows. This geological vulnerability transforms a standard rainstorm into a life threatening hazard, as the charred vegetation cannot anchor the soil, a risk that meteorologists warn will persist for years until the local ecosystem recovers.
Beyond the geological threats, the storm has wreaked havoc on critical infrastructure during one of the busiest travel weeks of the year. The Los Angeles Department of Water and Power reported over 10,700 outages caused by storm debris, while high winds clocked at 82 mph in some areas have forced road closures on major routes like the Angeles Crest Highway. With the San Francisco Bay Area also facing risks of offshore waterspouts turning into tornadoes, the National Weather Service is urging residents to avoid driving through flooded roadways, turning a holiday intended for celebration into a period of high alert survival.