High Winds Through Tuesday Will Worsen California’s Historic Wildfire Disaster

November 11, 2018, 3:25 PM EST

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Above: Sheriff's deputies recover the body of one of the victims of the Camp Fire on Saturday, Nov. 10, 2018, in Paradise, Calif. (AP Photo/Noah Berger)

Extremely dangerous fire conditions will continue to worsen a historic wildfire disaster in California through Tuesday, as fierce Santa Ana winds combined with exceptionally dry conditions continue. As of Sunday morning, the fires that began on Thursday have killed at least 25 people, caused over 250,000 to evacuate, and brought the state its most destructive fire in modern records.

At 10:24 am EST Sunday, Cal Fire reported over 6700 structures were destroyed by the Camp Fire, mostly in the Northern California town of Paradise (population 27,000). This makes it the most destructive fire in California history. The previous record was the 5636 structures destroyed just last year in the Tubbs fire of October 2017. The Camp Fire was 25% contained, threatened 15,000 structures, and had burned 109,000 acres as of 10:24 am EST Sunday. The 23 deaths from the fire make it the third deadliest in California history.

The Woolsey Fire, which rampaged across the Malibu area and other parts of Ventura and Los Angeles counties on Friday, has destroyed at least 177 structures, according a Cal Fire update at 11:48 am EST Sunday. The fire has consumed 83,275 acres and was just 10% contained. Two deaths and three firefighter injuries have been attributed to the fire. "Crews will continue to battle steep terrain, limited access, and extreme fire behavior," warned Cal Fire. Some 57,000 structures were still threatened by the Woolsey Fire.

A few miles to the west, the Hill Fire was 70% contained after torching more than 4500 acres and two structures, Cal Fire reported.

Capt. Adrian Murrieta (Los Angeles County Fire Department) hoses down hot spots on a wildfire-ravaged home Saturday, Nov. 10, 2018, in Malibu, Calif
Figure 1. Capt. Adrian Murrieta (Los Angeles County Fire Department) hoses down hot spots on a wildfire-ravaged home Saturday, Nov. 10, 2018, in Malibu, Calif. Scores of houses from ranch homes to celebrities' mansions burned in a pair of wildfires (the Woolsey Fire and Hill Fire) that stretched across more than 100 square miles of Southern California, authorities said Saturday. (AP Photo/Marcio Jose Sanchez)
Fire weather outlook
Figure 2. Day 1 and Day 2 weather outlooks for the 24 hours ending 7 am EST Monday, November 12 (left) and 7 am EST Tuesday, November 13 (right), issued by the NOAA/NWS Storm Prediction Center on Sunday morning, November 11, 2018. An “Extremely Critical” fire weather area--the highest level of danger--was outlined for the Los Angeles area both days, extending southwards to the San Diego area by Day 2. “Critical” fire conditions were outlined for the Northern California regions devastated by the Camp Fire for Day 1, with conditions improving to an “Elevated” risk by Day 2. Image credit: NOAA/NWS/SPC.

Another round of extreme fire weather

The next several days will be a grueling period for California firefighters and residents, especially in the hilly terrain stretching from Santa Barbara to San Diego. An upper-level low settling into the central U.S. is pushing a surface high into California, much like the one that triggered high winds on Thursday. The air making its way into the state from Nevada is exceptionally dry. The 12Z Sunday morning sounding held just 0.10” of precipitable water at Reno, NV, and 0.13” at Las Vegas, which is about a third of the average amount for this time of year. As this air is pushed over California’s mountain ranges, it will warm upon descent, and the relative humidity will plummet to the 5% range in some areas. Temperatures across California will not be extremely warm the next several days—in part because the widespread smoke will block solar heating—but the air is so dry that relative humidity will still be very low.

Widespread 40 – 50 mph gusts may work their way through the day Sunday into the western Sierra Nevada foothills, including the area north of Sacramento where the Camp Fire is still raging. Gusty conditions will extend across many other parts of northern California, including the North Bay Mountains and East Bay Hills near San Francisco. Winds in northern California should be on the decrease after Sunday night, and critical/extreme fire weather is not expected in the state’s northern half from Monday onward.

Southern California will have a more prolonged siege of fire-conducive weather. Santa Ana-type offshore winds will be pushing through the passes of coastal mountains, with sustained winds of 20 – 30 mph and gusts to 40 – 60 mph expected to develop Sunday afternoon, perhaps across the Woolsey Fire area. The Santa Ana winds may actually intensify on Monday and peak on Tuesday, and weaker offshore flow is expected to continue into Wednesday. The fire weather threat will also be spreading southward from the Los Angeles area: by Monday, top-end “extremely critical” conditions are predicted by NOAA/SPC to extend all the way to the U.S. Mexico border east of San Diego. No rain is expected in California until November 17 at the very earliest.

Figure 2. The Air Quality Index (AQI) from wildfire smoke was in the red “Unhealthy” range (above 150) over much of California on Sunday, with a few stations reporting purple “Very Unhealthy” (above 200) conditions for fine particulate pollution (PM2.5). At this level, the EPA warns PM2.5 can cause “Significant aggravation of heart or lung disease and premature mortality in persons with cardiopulmonary disease and the elderly; significant increase in respiratory effects in general population.” One station near Sacramento had air quality that was even worse, in the maroon “Hazardous” range. Image credit: EPA.

Dangerous air quality in California

Smoke from the Camp Fire has drifted over most of California, bringing dangerously high levels of fine particulate pollution (PM2.5, particles less than 2.5 microns or 0.0001 inch in diameter). Hourly levels of PM2.5 were in the red “Unhealthy” range at official EPA monitors across much of the San Francisco Bay and Los Angeles areas on Sunday afternoon, with a few stations reporting purple “Very Unhealthy” conditions and one station in the maroon “Hazardous” range.

In Chico, downwind of the Camp Fire, PM2.5 levels hit an insane 995 μg/m3 for three hours on Friday evening, and the 24-hour PM2.5 level averaged out to 280 μg/m3 for the day. That’s eight times higher than the 24-hour PM2.5 standard of 35 μg/m3, and well into the maroon “hazardous” range—the highest level of danger on EPA’s Air Quality Index (AQI) scale. At this level, EPA warns that “this would trigger a health warnings of emergency conditions. The entire population is more likely to be affected by serious health effects.” Friday’s pollution in Chico was by far the highest 24-hour PM2.5 measurement in in the city going back to at least 1999, when on-line records from EPA start; the previous record was 107.6 μg/m3 In 2008. Things were not much better on Saturday, which came in with a 24-hour PM2.5 level of 243 μg/m3--in the purple “very unhealthy” range.

Wildfire smoke contributes to thousands of deaths each year in the U.S.

The tragic burning and asphyxiation deaths of 25 people in the latest California wildfires are just a small fraction of the deaths these fires are likely to bring, unfortunately. Air pollution from the fires are bound to cause hundreds more premature deaths, given the large population that is being exposed to dangerous levels of choking smoke. A July 2018 paper by Colorado State's Bonne Ford and co-authors estimated that wildfire smoke contributed to 17,000 premature air pollution deaths per year, on average, in the U.S. in the year 2000. This number was projected to rise to 44,000 deaths per year by the year 2100, if we follow a “business-as-usual” approach to climate change (RCP8.5 scenario), which would lead to a steady increase in U.S. wildfires.  A premature air pollution-related death typically occurs about twelve years earlier than it otherwise might have.

Climate change and this autumn’s California fires

Daniel Swain, author of the California Weather Blog, fired off a superb tweetstorm on Saturday drawing the links between our evolving climate and California’s fire threat. One of the key elements in the multiple massive autumn fires of 2017 and 2018 has been extreme levels of landscape-drying summer heat followed by a delayed start to the winter wet season.

“While autumn precipitation isn't usually huge fraction of overall annual average, it's hugely important to ecosystems & in bringing 'fire season-ending' moisture. This yr, autumn precip was <20-30% of avg,” tweeted Swain. His own work shows that a state trend toward hotter drought periods and drier autumns will continue as human-produced climate change continues. Strong winds in autumn—a natural part of California’s climate—will thus carry a higher risk of exacerbating blazes.

“In many cases, human factors like human encroachment/urban development in high fire-risk wildlands is at least as important as climate change. In other cases, forest and fuels management is also key consideration.” Swain added. “But on top of these other factors, climate change is acting as a pervasive and growing ‘wildfire threat multiplier’.”

Bob Henson co-wrote this post.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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