Santa Ana winds are notorious for rapidly advancing fires in Southern California, pushing embers far beyond the fire line and across neighborhoods and major roads.
But officials say the winds that sparked devastating fires in three areas of Los Angeles County were far more erratic and unpredictable than typical dry offshore wind patterns, making them more susceptible to such events. He said the attack struck an area he was unfamiliar with.
A life-threatening storm that triggered days of dire warnings evolved into a more serious crisis than firefighters expected, with embers flying in all directions an estimated two to three miles ahead of the ignited fire.
Extreme winds have created extreme fires that are almost unpredictable, disrupting efforts to establish safe containment lines and utilize firefighting aircraft. It has also caused massive structural losses, widespread evacuations, and ongoing destruction.
“Typically, as conditions continue in Santa Ana, fires develop in strips,” Los Angeles County Fire Chief Anthony Malone said. “But with these unstable winds and this PDS, or particularly dangerous conditions, the wind direction was constantly changing.”
In addition to the long-range observations typical of such offshore wind events, Marrone said embers flew in different directions, sometimes changing paths throughout the day. The large wildfires spread seaward, as is common during the Santa Anas season, but the fires were growing laterally, he said.
“This was completely different,” Marrone said.
The Palisades Fire, which started early Tuesday morning, has destroyed more than 1,000 structures in Pacific Palisades, and its area has ballooned to more than 15,000 acres as of Wednesday afternoon. The Eaton Fire broke out late in the day, but quickly spread to Altadena and Pasadena, exploding over 10,000 acres and destroying at least 100 buildings. At least five people died in the Eaton fire.
In Sylmar, the Hearst Fire grew to 700 acres.
More than 65,000 people have been ordered to evacuate due to three fires, and thousands more have been warned they could be next in line. According to fire officials, there was no way to extinguish all three fires.
“This wildfire had some of the most chaotic winds I’ve experienced in 20 years,” Los Angeles Fire Department spokesman Capt. Eric Scott said of the Palisades fire. He said the 2018 Woolsey Fire, which burned nearly 100,000 acres in southeastern Ventura County and Malibu, destroyed 1,500 structures and killed three people, was the only one in Southern California with winds approaching it this week. He said it was a fire.
“With these chaotic winds blowing, we were absolutely concerned that we were going to have an explosive fire like this,” Scott said. “It’s not just the fire front that destroys a home; it’s the embers that can fly a mile or two forward and land on a property or get into someone’s attic and burn a home from top to bottom. ”
In areas where such explosions are rare, the gusts occur at dangerously high speeds.
Forecasters warned of an event that could produce brief but highly destructive winds, especially in the San Gabriel Valley and foothills. Rich Thompson, a meteorologist with the National Weather Service, said this “mountain wave wind” activity gains momentum when gusts move quickly down mountain slopes and hit flat terrain, resulting in “short periods of very strong and dangerous winds. He said the wind speed could reach 80 degrees during the “hourly blowout” phenomenon. 100 miles per hour.
That was spot on. Wind gusts exceeding 160 mph were observed late Tuesday into Wednesday morning, including one near Altadena that reached 160 mph at 5 a.m., the weather service said. Meteorologist Rose Schoenfeld said Wednesday morning that these extreme wind gusts were likely caused by “mountain wave wind” activity.
Neil Lareau, a professor of atmospheric science at the University of Nevada, Reno, said on social media that the winds around the Eaton Fire were “gusting strong,” strong enough to sweep up and down the San Gabriel Mountains. said. In contrast, the less extreme Santa Ana wind flow is partially blocked and ends up flowing through the canyon and through the so-called Santa Ana wind corridor.
It didn’t help that the area hadn’t seen any significant rain in eight months, which was in the lead-up to the wildfires.
“We’ve had so much rain and snow over the last few years that we’ve had a lot of excess fuel and it’s been very dry,” said Tirtha Banerjee, an associate professor of civil and environmental engineering at the University of California, Irvine. he said. “Then we had a weather system that produced very fast-moving Santa Ana winds.”
Banerjee’s research found that these strong wind gusts help carry embers up the attic and are “the cause of most of the building damage,” he said.
“It’s not always this big wall of flame, it’s the embers being carried over long distances and landing on some type of fuel nearby, or landing directly on a building.”
During heavy rainstorms, embers are a deadly intruder into homes. Embers that are pushed through small openings or hit exposed wood by strong winds can ignite the majority of home fires. In the 2007 Witch Fire, embers often smoldered for several hours before burning through homes.
Firefighters say past firestorms have sometimes destroyed homes from the inside, a clear sign that the fires were caused by internal embers rather than flames attacking the exterior walls.
Houses burned with embers can also contribute to the creation of more embers, Banerjee said. This is a common phenomenon in wildland-urban interface fires, often caused by a combination of structure and vegetation fires.
Santa Ana winds occur regularly this time of year, but particularly strong gusts can pick up speed and blow in unpredictable ways as they blow through complex terrain and topography, the nonprofit conservation organization says. said Alexandra Shipherd, senior research ecologist and adjunct at the Institute of Biology. Professor at San Diego State University.
“When you have winds like this, the fire no longer spreads to the vegetation on the ground,” she said. “The fire is spreading through the air.”
The ember nature of wildfires may help explain why homes continue to stand next to gutted ones in some areas. By carefully sealing openings through which embers can enter, more fire-resistant homes have a better chance of surviving embers clouds.
Noah Diffenbaugh, a climate scientist at Stanford University, said it’s difficult to say exactly what role climate change played in these wildfires, but it’s possible that they could spread so dramatically. He said the contributing climate conditions were consistent with what scientists expect in a warming world.
“There is clear evidence that not only the Earth is warming, but California is warming,” he said. “We know that warming temperatures increase the likelihood of highly flammable plants.”
Research shows that human populations are increasing in virgin urban edges, especially in areas where vegetation is highly susceptible to climate change, Diffenbaugh said.
“So the areas that are most sensitive in terms of wildfire risk have this kind of dual risk of climate change and population growth,” he said.
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