Tropical Storm Hilary Douses Southern California with Rare Flooding Rains

A dangerous tropical system is unleashing torrential rainfall and damaging winds across Southern California, as the remnants of Hurricane Hilary crash ashore with life-threatening flooding potential. After slamming Mexico's Baja Peninsula, Hilary tracked north into the US Southwest Sunday, becoming the strongest tropical storm to directly hit Southern California since 1939.

Photo by Chris Gallagher on Unsplash

With its center located near Palm Springs Sunday evening, Hilary is forecast to move across inland areas overnight before dissipating over Nevada by Monday morning. But tremendous amounts of tropical moisture will wring out ahead of the system’s path, triggering historic rainfall rates and catastrophic flash flooding through daybreak.

Riverside, San Bernardino, Los Angeles, and San Diego counties have all declared emergencies, with widespread evacuations ordered. Hilary’s heavy rains fall on already saturated ground, meaning excessive runoff capable of washing away vehicles, homes, and people in its path. Residents are urged to shelter in place through Monday morning, avoiding roads that may suddenly flood or collapse amid the extreme deluge.

The National Weather Service warns isolated areas could witness over 10 inches of rain, more than their entire yearly average, within just 12 hours. Hillside neighborhoods face the highest risk of mudslides and fast-moving debris flows, which can strike with little notice during intense downpours. Howling winds will add to the hazards by toppling trees and power lines, causing widespread outages.

Lacking modern storm safeguards and infrastructure, Southern California remains highly vulnerable to Hilary’s remnants. The last comparable tropical system 80 years ago killed several people and destroyed homes as rivers jumped their banks. While forecasting abilities have improved dramatically since 1939, millions more now live in harm’s way, underscoring this storm’s unprecedented threats.

Hurricane Hilary Wallops Mexico before Menacing US with Flooding Rains

The non-stop downpours arrive in the wake of Hurricane Hilary’s earlier landfall over Baja California, Mexico, bringing deadly flooding, fierce winds, and extreme beach erosion. At least one drowning fatality occurred in the coastal town of Santa Rosalia amid collapsed buildings and swamped roads. While weakening before impacting Southern California, abundant moisture will keep Hilary a dangerous and historic flooding threat.

Packing winds over 100mph offshore last week, Hurricane Hilary formed in the active Eastern Pacific on July 24th before peaking in intensity south of Baja California. But the storm rapidly weakened over cooler waters near Mexico, diminishing from a Category 2 to tropical storm status this weekend before turning north toward the US coastline. Despite lower winds, Hilary still contains copious rainfall that now threatens America’s Southwest.

Remnant moisture from past East Pacific hurricanes has spawned some of Southern California’s worst flooding disasters. In 1976 and 1984, dissipating storms brought tremendous rainfall that sent hillsides sloughing down into neighborhoods, killing dozens. With much higher prior wind speeds than those storms, Hurricane Hilary could unleash even greater hazards now that it has California and the Southwest in its crosshairs.

Evacuations Ordered as Hilary’s Onslaught Floods Roads, Triggers Blackouts

In anticipation of Hilary’s dangerous impacts, California’s governor declared a state of emergency Saturday evening encompassing eight counties in the tropical storm’s path. Hardest hit zones are predicted from San Diego northeastward to Death Valley, where flooding could rapidly overwhelm first responders. Mandatory evacuation orders were issued for many communities at high risk of deadly mudslides and debris flows.

As outer rain bands swept through Sunday, flooded roads and highways stranded vehicles while rising waters seeped into homes and businesses. Some Los Angeles freeways became raging rivers, nearly sweeping away trapped cars. With drainage systems overwhelmed, officials pleaded with residents to avoid driving into floodwaters, which can conceal washed out roads and quickly stall engines.

Gusty winds downed trees and power lines Sunday evening, cutting electricity to tens of thousands as the worst conditions approached. Weakened trees and soils saturated by earlier rains mean more trees are likely to topple overnight, expanding power outages across the region. With phones and laptops lacking charge, individuals should conserve device batteries in case of emergencies.

Prepare Now Before Hilary’s Overnight Onslaught Arrives

Residents are advised to urgently complete storm preparations Sunday evening before intense rainfall arrives overnight. Shelter pets and move vehicles to high ground immune from flooding. Ensure flashlights, batteries, and battery-powered radios are available in case power is lost. Stock up on enough non-perishable foods and water to last several days without electricity.

Know if your area is under evacuation orders and have a plan to leave immediately if called to do so. Avoid walking or driving through floodwaters, which can conceal deadly hazards and wash people away. Remain inside secure shelters like upper floors instead of venturing out during the storm’s peak intensity.

With heavy tropical rains after dark, stick to main routes and avoid driving if possible. Just 12 inches of fast-moving water can sweep away cars. If trapped by rising waters, immediately abandon vehicles and seek higher ground. Charge devices now so phones can be used to call 911 or check storm updates if power fails overnight.

Through diligent preparation and accurate warnings from the National Weather Service, Southern California aims to weather this unprecedented tropical emergency with minimal loss of life and property damage. But all residents must take Hilary’s threats seriously and exercise extreme caution over the next 24 hours, as the storm unleashes its full fury overnight.

Last Major Tropical Storm Impact was Devastating 1939 Cyclone

Southern California’s lack of tropical storm experience adds to Hilary’s hazards. The last significant impact came in September 1939, when an unnamed tropical cyclone took a similar path after striking Baja California. That storm brought torrential rainfall and destructive winds over 3 days, killing several people and destroying homes.

In 1939, weather forecasting technology was primitive compared to today’s satellite data, radar networks, and predictive models. Yet the region’s population was a small fraction of today’s tens of millions, meaning many more residents now occupy vulnerable areas downstream of channels, canyons, and cliffs. Legacy infrastructure never designed for tropical events further compounds modern risks.

In recent decades, the region has contended with tropical moisture from decaying East Pacific hurricanes or their remnants. In 1976 and 1984, storms crossing northwest Mexico brought extreme rainfall causing deadly landslides and debris flows in California. But with its formidable wind speeds offshore, Hilary has much greater flooding potential than those past events.

Adapting to the New Climate Reality of Megastorms

While no stranger to cycles of drought and wildfires, Southern California lacks modern infrastructure and planning adapted for tropical deluges worsened by climate change. Storms like Hilary represent the region’s future as global warming intensifies precipitation and floods worldwide.

Warming oceans provide more fuel for tropical cyclones, allowing them to generate far greater rainfall. Recent research shows hurricanes are moving slower post-landfall, stalling over areas for days rather than dissipating quickly. Slower storms dump more rain locally, as seen during Hurricane Harvey’s catastrophic flooding of Houston in 2017.

Even as Hilary weakens over land, its tropical moisture will wring out over Southern California, demonstrating how future storms will require major investments in flood control, dams, levees, and stormwater systems. Emergency managers also need enhanced plans to evacuate millions living in flood zones. Adapting to the new climate reality means being ready for megastorms like Hilary.

Through Monday Morning, Focus is on Surviving Hilary’s Onslaught

For now, Southern California’s full attention rests on surviving the next 12 hours of Hilary’s expected onslaught. Listen closely for evacuation orders in your area and don’t chance driving on any flooded roads. Check on neighbors to ensure they are prepared and assist each other however possible.

With experts likening Hilary to a 500 or even 1,000-year flood event, the time to prepare is before night falls and the most dangerous conditions arrive. Experienced hurricane regions know the keys are vigilance, cooperation, and advance planning – all urgently needed in Southern California as this rare tropical threat nears peak intensity overnight. Stay safe and listen for further weather alerts. By working together, we can overcome any challenge, even historic storms like Hilary.

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