A wind-driven wildfire roared through rural and residential communities north-west of Los Angeles, charring more than 20,500 acres and leveling scores of homes.
The Mountain fire in Ventura county, California, continued to burn on Thursday morning, as footage showed dozens of structures turned to smoldering ruins now lining the streets where neighborhoods once stood.
Fire officials said in a news conference on Thursday evening that an assessment by damage teams has revealed 132 structures destroyed, mostly homes, and 88 structures damaged.
“This is a challenging fire and a wind-driven fire. We are still at 0% containment as we are still focusing on life safety and structure defense,” said a Ventura county fire spokesperson, Andy VanSciver, in a morning press conference, adding that the county has deployed 10 damage assessment crews to go street-by-street to tally the toll. By Thursday evening, the fire was 5% contained.
Hundreds of firefighters battled the blaze through the night using both ground resources and helicopters, according to the Ventura county fire department, and officials added more resources were on the way.
Fueled by strong winds with gusts up to 85mph (187km/h) and humidity levels as low as 8%, the fast-moving fire gave residents little time to flee on Wednesday, causing frenzied evacuations of more than 10,000 people. Roughly 3,500 homes and businesses remain under threat, according to officials.
Many large animals were in need of rescue as well, as equestrian groups coordinated efforts online to secure trailers and stalls as fairgrounds and other evacuation areas filled.
The Santa Anas, warm, dry winds that typically whip through southern California this time of year, were not unexpected. But back-to-back years of strong rainy seasons seeded these landscapes with grasses that turned to tinder after getting baked in the summer heat. Combined with low humidity and this region’s natural tendency to burn, the perfect recipe was set for the disaster to unfold.
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“The Mountain fire is another sobering reminder that when you combine our natural chaparral landscapes and strong Santa Ana winds with longer, hotter dry seasons, you have all the ingredients for these devastating events to increase in frequency, scale and speed,” said Dr Alex Hall, director of UCLA’s Center for Climate Science, in a statement.
“Unfortunately, it’s never a question of ‘if’ but rather ‘when’ and ‘how big’ when it comes to wildfires in southern California.”
By Thursday morning, the National Weather Service reported that relative humidity was as low as 10%, with wind gusts of 60mph in certain areas. High wind warnings and dense smoke advisories are in effect for certain regions on Thursday.
The red flag warning will remain in effect in most areas through much of Thursday and will extend into Friday morning for the same regions including the inland empire, the coastal slopes of San Bernardino county, and the mountain areas of San Diego and Riverside county.
Drew Smith, assistant chief of the LA county fire department, said the conditions prompting the red flag warnings were responsible for the fire’s exponential growth, describing how the blaze spit embers that moved flames up to three miles ahead. “It makes it very challenging for our firefighters to combat these fires,” he said.
But in a Thursday morning update, the NWS said conditions around where the fire was burning had improved from the day before.
The particularly extreme red flag condition forecast for the area, characterized by critically dry fuels, low humidity, and strong winds, “had moderated a little bit”, according to Rich Thompson of the NWS, who spoke to reporters on Thursday. “Fortunately by mid-to-late afternoon we expect the Santa Ana winds to diminish in strength,” he added. “By 6pm this evening we expect the red flag conditions to end across the area.”
US wildfire terms, explained
ShowAcres burned
US wildfires are measured in terms of acres. While the size of a wildfire doesn’t necessarily correlate to its destructive impact, acreage provides a way to understand a fire’s footprint and how quickly it has grown.
There are 2.47 acres in a hectare, and 640 acres in a square mile, but this can be hard to visualise. Here are some easy comparisons: one acre equates to roughly the size of an American football field. London’s Heathrow airport is about 3,000 acres. Manhattan covers roughly 14,600 acres, while Chicago is roughly 150,000 acres, and Los Angeles is roughly 320,000 acres.
Megafire
A megafire is defined by the National Interagency Fire Center as a wildfire that has burned more than 100,000 acres (40,000 hectares).
Containment level
A wildfire’s containment level indicates how much progress firefighters have made in controlling the fire. Containment is achieved by creating perimeters the fire can’t move across. This is done through methods such as putting fire retardants on the ground, digging trenches, or removing brush and other flammable fuels.
Containment is measured in terms of the percentage of the fire that has been surrounded by these control lines. A wildfire with a low containment level, such as 0% or 5%, is essentially burning out of control. A fire with a high level of containment, such as 90%, isn’t necessarily extinguished but rather has a large protective perimeter and a rate of growth that is under control.
Evacuation orders and warnings
Evacuation warnings and orders are issued by officials when a wildfire is causing imminent danger to people’s life and property. According to the California office of emergency services, an evacuation warning means that it's a good idea to leave an area or get ready to leave soon. An evacuation order means that you should leave the area immediately.
Red flag warning
A red flag warning is a type of forecast issued by the National Weather Service that indicates when weather conditions are likely to spark or spread wildfires. These conditions typically include dryness, low humidity, high winds and heat.
Prescribed burn
A prescribed burn, or a controlled burn, is a fire that is intentionally set under carefully managed conditions in order to improve the health of a landscape. Prescribed burns are carried out by trained experts such as members of the US Forest Service and Indigenous fire practitioners. Prescribed burns help remove flammable vegetation and reduce the risk of larger, more catastrophic blazes, among other benefits.
Prescribed burning was once a common tool among Native American tribes who used “good fire” to improve the land, but was limited for much of the last century by a US government approach based on fire suppression. In recent years, US land managers have returned to embracing the benefits of prescribed burns, and now conduct thousands across the country every year.
As conditions improve – and especially as winds slow – firefighters will be much better able to begin corralling the blaze.
“Our firefighters are doing nothing short of heroic out there right now,” Trevor Johnson, Ventura county fire department captain, said on Wednesday, noting the extreme and dangerous firefighting conditions.
Due to the high fire danger, Southern California Edison temporarily turned off power to several thousand customers as part of its public safety power shutoff plan to prevent the electric system from becoming a source of ignition.
Similarly, the Pacific Gas and Electric Company cut power to thousands of accounts across the state in an attempt to limit the risk of ignitions.
As of Thursday morning, about 3,000 customers were without power in Ventura county and just over 500 were without power in Los Angeles county, according to poweroutage.us.
Ventura county schools also announced that all schools in the area would be closed on Thursday and Friday.
Gavin Newsom, California’s governor, announced on Wednesday that the state had secured federal assistance from the Federal Emergency Management Agency to help ensure the availability of vital resources to Ventura county.
“This is a dangerous fire that’s spreading quickly and threatening lives,” Newsom said. “State resources have been mobilized to protect communities, and this federal support from the Biden-Harris administration will give state and local firefighters the resources they need to save lives and property as they continue battling this aggressive fire.”
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As the climate crisis turns up the dial, creating new hazards and higher risks for disasters like the Mountain fire, scientists are hoping lessons can be learned.
“Until now, much of the research around managing wildfire risk in California has focused on forested areas, but the Mountain fire once again drives home the urgent need for strategies tailored to the unique landscape, climate and communities of southern California,” Hall said.
“We hope that our work can provide policymakers with the solutions-oriented research they need to make the best decisions to protect our communities and our environment in the face of a changing climate.”
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