What to anticipate within the coming months
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California already has a historic year for wildfires.
So far, 1.66 million hectares have been burned – an area five times the size of the city of Los Angeles. Almost no part of the state is untouched. From the Santa Cruz Mountains to Riverside County, the slopes of Mount Hamilton to the Napa Valley and the northern Sierra, 15,800 Florida and New Jersey firefighters are fighting two dozen major fires, many of which were triggered by rare thunderstorms two weeks ago.
And although the fire brigade is finally gaining the upper hand with many, fire experts have a clear message: This year is particularly dry and the worst could still come.
“We’re approaching the peak of the fire season,” said Daniel Berlant, a spokesman for Cal Fire, the state’s main fire service.
There are at least two more months, and possibly three more, during which the risk of huge new fires will continue to increase, before the autumn rains hit. And 2020 has seen the second most acres burned in a year in modern history, after just 2018 when 1.97 million hectares were burned.
“It’s so important that we get public help,” said Berlant. “We have been incredibly busy the past two weeks. These were fires kindled by Mother Nature. We need people who can reduce the risk of man-made fires. “
An analysis of the precipitation patterns in autumn over the past ten years speaks for itself.
Using San Francisco as a proxy for Northern California, the first significant rain shower of half an inch or more in seven of the last 10 years did not occur until after November 15. That’s 11 weeks now. In the other three years it came on October 16 at the earliest. That’s another seven weeks.
“We hold our breath, so to speak, until we just get into the rainy season,” said Jan Null, a meteorologist at Golden Gate Weather Services in Half Moon Bay, who combed through the data.
“Just because current events are slowly subsiding doesn’t mean we won’t see more fires,” he said. “We are heading for what is usually the most dangerous part of the fire season.”
BOULDER CREEK, CA – AUGUST 19: Volunteer firefighters for the Boulder Creek Fire District view the direction of the fire before dispatching to fight the fire at the CZU August Lightning Complex on August 19, 2020 in Boulder Creek, California ( Dai News Group Sugano / Bay Area)
The past explains the future.
Eight of the ten deadliest fires of all time in California occurred in October or November, from the Camp Fire that killed 85 people in the city of Paradise in 2018, to the Wine Country Fires in Napa and Sonoma Counties in 2017 to Oakland Hills Fire in 1991.
Similarly, seven of the ten most devastating fires in California history, as measured by the number of houses burned, occurred in October or November.
Experts say that there are two main reasons: lack of rain and strong, dry wind.
Unlike most other states, it almost never rains in California in the summer. As part of California’s Mediterranean climate, most rainfall ends in April each year and, apart from a few light splashes, doesn’t really start again until November. This means that by October it was almost six months without rain.
Grass, bushes and trees are therefore usually the driest of the year in October.
Records show that most of California’s worst fire seasons, ranked by acres burned, come after a drier than normal winter. Why? In wet winters, there is more snow in the Sierra Nevada. The longer it lasts into summer, the less space there is to burn. And more rain means more moisture in the vegetation.
Unfortunately this year was a dry winter.
On April 1, the national snowpack in the Sierra was only 54% of its historical average. Last year it was 161%, and California ended up with a sub-par fire year with only 259,148 acres burned nationwide.
The same goes for rains. As of October 1, San Francisco received only 50% of historical average rainfall, San Jose 49%, Oakland 42%, and Sacramento 53%. In contrast, Los Angeles and San Diego had normal rainfall years and received 101% and 133% of their historical averages, respectively.
Simply put, conditions in Northern California are drier than normal, which has contributed to the explosive spread of the CZU, SCU, and LNU fires this month.
Craig Clements, director of the Fire Weather Research Laboratory at San Jose State University, called the thunderstorms in mid-August, which caused 12,000 lightning strikes and started around 700 new fires, a rare occurrence. California haven’t seen anything like it since 2008. People shouldn’t read too much into it as a predictor for the rest of the year, he said. Instead, they should look at the broader rainfall patterns, combined with a heat wave that much of the state suffered just before the fires, and daily measurements like overnight humidity.
“It’s crazy that we had so many ignitions at the same time,” said Clements. “For many it is apocalyptic. But it was a weather event. Let’s hope that this was the big event of the year. “
Huge amounts of dead bush, trees, and other vegetation, some killed during the state’s five-year drought and others piled up from decades of firefighting, are making the fires hotter and bigger.
Clements and his students regularly test the amount of water in chamois, a common flowering shrub, to determine the moisture content of the fuel.
In Quail Hollow Ranch County Park in the Santa Cruz Mountains near Ben Lomond, they found a moisture content of 67% on August 16. It was there in the middle of September last year. In other words, bushes and other vegetation in the Santa Cruz Mountains that are still burning are as dry now as they were a month later last year.
“We’re seeing fuel moisture levels that match our drought years,” he said. “Because we probably won’t get any rain for the next few weeks, these fuels will continue to be dry. And they are already critical. “
Climate change also plays a role. The world’s 10 hottest years, dating back to 1880 when modern temperature records began, have all occurred since 1998, according to NASA and NOAA, the parent agency of the National Weather Service. Hotter weather dries out vegetation earlier in the year, resulting in a longer fire season.
Add to this the strong “Santa Ana” winds in Southern California and “Diablo” winds in Northern California, which blow hot inland air over the state, increase the risk of fire and typically peak in October.
FAIRFIELD, CA – AUGUST 19: A Cal Fire Tanker drops fire retardant fabrics on a hill behind homes in the Rolling Hills neighborhood of Fairfield, California on Wednesday, August 19, 2020. Residents were ordered when the LNU Lightning Complex wildfire threatened the neighborhood. (Anda Chu / Bay Area News Group)
“We have a big fire season ahead of us. We call it the year of fire, ”said Robert Baird, director of fire and aviation management for the Pacific Southwest for the US Forest Service in Vallejo. “People shouldn’t let their vigilance down.”
Baird, whose own family was evacuated from their home near Vacaville for one night two weeks ago because of the LNU complex fire, said people across the state should remove the vegetation around their homes and have an evacuation plan and list create with objects they would take if they suddenly had to go because of an rampant fire.
“People need to look at red flag warnings as if they were tornado warnings,” he said. “They are a grueling combination of dry air, wind and heat. They can be murderers and have killed people. “
“If there is a fire on the ground,” he warned, “it will be too late to make your preparations.”
U.S. Forest Service firefighters clear debris from a steep slope as they tackle the Dolan Fire in Big Sur on Tuesday, August 25, 2020. (David Royal / Monterey Herald Correspondent)
