© Provided by The LA Times
The Creek Fire approaches Shaver Lake in Fresno County on September 6. (Kent Nishimura / Los Angeles Times)

The West Coast had just experienced a record heat wave when news broke last week of a rare late summer blizzard in Colorado. For those still suffocating in California, Oregon, and Washington, it sounded like a dream come true. In fact, it was a harbinger of a greater disaster to come.

When the blast of cold air in the Rocky Mountains sank, he looked for an escape: the warmer-climate lands to the west, toward the Pacific coast. That unleashed raging winds that spilled over the Sierra Nevada and Cascade mountain ranges, acting like a giant bellows across the entire Pacific coast, where fires were already burning in brush and dry wood.

The result: an epic firestorm stretching from the borders of Mexico to Canada that has killed dozens of people, swept through entire towns and caused the worst air pollution ever seen in the region.

For California, it is the second time in a month that a series of unfortunate weather conditions have aligned in a way that has caused wildfires to spread at record speed. The rapid spread of fire was compounded in part by climate change, which not only makes temperatures higher, but is also blamed by some scientists for causing dry spells to get even drier while wet spells become even drier. they become more humid, which makes the vegetation even more mature to light.

In Oregon, too, where at least 10 have died and officials prepare for a « mass death incident » as they search for the missing, there was no precedent in the modern record for the sheer number and scale of wildfires. The losses in Washington have been the second worst in the history of that state.

So far this year, the fires have burned more than 3.3 million acres in California, more than 1 million acres in Oregon, and more than 625,000 acres in Washington state.

California last broke its record for its largest wildfire season just two years ago, when more than 1.8 million acres were burned.

The unprecedented nature of today’s fires stems from the extreme cold that began to hit the Rocky Mountains on Labor Day. It caused the cold air to sink in, increasing the air pressure on the surface; At the same time, the heat on the West Coast caused the hot air to rise, lowering the air pressure on the ground, according to Rebecca Muessle, a meteorologist with the National Weather Service office in Portland, Oregon.

And since the winds flow from high pressure areas to low pressure areas, that sent strong winds from east to west.

Many Californians know these events as the Santa Ana or Devil’s Winds; meteorologists in Oregon and Washington call them offshore wind events or easterlies. Whatever its name, last week’s wind event « was particularly strong, much stronger than a typical ocean wind event, » said meteorologist Connie Clarstrom of the National Weather Service office in Medford, Oregon. « It is very rare to see winds as strong as the ones we saw in that case. »

In southern Oregon, gusts of up to 45 mph hit Jackson County’s Rogue Valley from the Cascade Mountains, spreading the Almeda fire, crushing the cities of Phoenix and Talent southeast of Medford, leaving at least four dead and one missing. . A 41-year-old man, Michael Jarrod Bakkela, has been arrested on suspicion of arson.

Southeast of the state capital of Salem, houses along Santiam Canyon caught fire, causing at least four deaths in Marion County, including those of a 13-year-old boy and his 71-year-old grandmother in the city. Lyons and 10 missing. The Beachie Creek fire had initially been small, less than 500 acres, and had been burning since Aug. 16. Just when the historic high-wind phenomenon began, the fire grew overnight to more than 131,000 acres. East of Eugene, Oregon, the Holiday Farm fire in Lane County that charred the McKenzie River Valley has claimed at least one life in the City of Vida and razed sections of the City of Blue River.

In far northern California, 63 mph gusts struck the Slater Fire in Siskiyou County; two people were killed in the Happy Camp community along the Klamath River in the Klamath National Forest, and 150 houses were destroyed.

In California, the difference in air pressure on both sides of the Sierra Nevada sent gusts of up to 60 mph through gaps in the state’s largest mountain range. That caused what had been a dying Bear fire, part of the North Complex fire zone in Butte, Plumas and Yuba counties, to begin to spread at a staggering 2,000 acres per hour.

“When we have that downhill wind, it is very dry. As the air descends in height, it actually warms up and dries out. And fires love dry conditions, ”said Cory Mueller of the National Weather Service in Sacramento. In addition to drying out, the air rushing over mountain peaks and slopes is accelerated by being forced through narrow canyons.

At least 14 deaths have been reported in Butte County, devastated by the Bear Fire. That fire was one of many in California caused by lightning in mid-August.

The Creek Fire, which ravaged the Sierra National Forest in Fresno and Madera counties, initially spread rapidly for a different reason.

Winds were normal on September 4, when the fire started. But the next day, « that fire impacted the materials it liked » and grew rapidly, creating an imposing cloud, called a pyrocumulonimbus of smoke and moisture that was pushed up into the sky so huge that it resembled the giant clouds seen when A storm is developing, according to Cindy Bean of the Hanford office of the National Weather Service.

At some point, that column of air and smoke became so heavy with the water vapor that it collapsed downward, creating a downdraft of air directed at the ground and spreading the winds rapidly over the surface. “When that column collapses,” Bean pointed out, “the wind comes straight down and then spreads everywhere. That allowed the fire to spread in many directions at the same time. « 

This rapid spread of the fire forced the evacuation of hundreds of campers by helicopter from the mountains, whose only road trip was cut off by the flames.

Then, after Labor Day, the same Santa Ana-style winds that hit Northern California and Oregon also hurtled through the canyons of the Central Sierra. In this part of California, they are called Mono winds, because they blow from the Mono Lake area, and sent 40 mph gusts from the northeast through the San Joaquin River canyon, helping push the Creek fire into communities. from Auberry and North Fork, Bean said.

In Los Angeles County, firefighters were concerned that the same Santa Ana winds from the northeast would send flames from the Bobcat fire in the San Gabriel Mountains to foothill suburbs like Altadena, Arcadia, Bradbury, Duarte, Monrovia, Pasadena and Sierra Madre. Late last week, the fire began to burn to the north, away from cities, although new evacuation orders were issued on Sunday when dangerous wildfire conditions returned.

Fortunately, the Santa Ana winds ended up not as strong around the El Dorado fire in San Bernardino County, an incident triggered by a pyrotechnic device used during a gender reveal party in Yucaipa, he said. Brandt Maxwell, a meteorologist with the San Diego office of the National Weather Service.

The location of the El Dorado fire turned out to be protected from the Santa Ana winds in the mountains, and the strongest winds in southern San Diego County bypassed where the Valley fire was burning, Maxwell said.

Interestingly, the oppressive smoke that litters the skies is helping firefighters in some parts of California.

The smoke is so dense that much sunlight cannot reach the surface and bounces off the layer of smoke in the air. That has resulted in cooler temperatures, helping firefighters in the Creek and Bobcat fires.

In the San Francisco Bay Area, a marine layer of low cloud and fog helped keep the hot, dry Diablo winds away from the region in recent days, which is close to containing the LNU lightning complex fires, SCU and CZU, said Rick Canepa of the National Weather Service office in Monterey. And the dense smoke, which resulted in an apocalyptic-looking dark orange glow in the skies over San Francisco last week, brought temperatures about 20 degrees below what had been forecast.

To read this note in Spanish, click here