The Real Story Behind the California Wildfires

By Paul Homewood

Meteorologist Cliff Mass has the real story behind the recent tragic wildfires in Northern California:

There has been a huge amount of media coverage regarding the tragic northern California fires, documenting the terrible loss of life and billions of dollars of damage to buildings, infrastructure, and the economy. As I write this, the death toll has risen to 41, over 5000 buildings have been destroyed or damaged, and the estimates of the financial loss are in the tens of billions of dollars.

Media stories have blamed the catastrophic fires on many things: a dry environment after the typical summer drought, unusual warmth the past several months, excessive rainfall producing lots of flammable grass, strong winds, global warming, and the lack of vegetative maintenance (clearing of the power lineright-of-ways) by the local utility (PG&E).

But none of the stories I have read get at what I believe is the real truth behind this unprecedented, severe, and explosively developing wildfire event:
A unique mountain-wave windstorm produced the strongest winds in the historical record at some locations. An event produced by the unlucky development of just the right flow regime that interacted with regional mountains to produce extreme winds beyond contemporary experience.
In short, this blog will make the case that the extreme nature of the wildfires were the result of a very unusual weather event, one that our weather models had the ability to forecast and warn about, if only their output were applied more effectively. The blog also suggests that better use of state-of-the-art weather prediction offers the hope of preventing a similar tragedy.

The Unique Wind Event
Although there have been a lot of media reports about windy conditions, few have described the extreme, often unprecedented, nature of the winds on Sunday night and Monday morning (October 8/9th). Some have even mocked PG&Es claims of hurricane-force winds, suggesting wind speeds of 30-40 mph.

Let’s clarify a few things. There was a wide range of winds that night, with the strongest winds on ridge tops and on the upper lee slopes of terrain. Some winds was startling.
For example, at 10:30 PM on 9 Oct 2017 the wind gusted to 96 mph on a 3400 foot peak NE of Geyersville, about 20 miles NNW of downtown Santa Rosa. They reported sustained 74 knots (85 mph). Those are hurricane force winds (sustained of 64 knots or more).
At the Santa Rosa RAWS station (U.S Forest Service and Bureau of Land Management) at 576 ft elevation, the wind accelerated rapidly Sunday night to 68 mph (see below).

What is really amazing about the winds at these sites, was that they were unprecedented: the strongest winds on record, with records going back to 1991 (Santa Rosa) or 1993 (Hawkeye). And we are not talking about winds during the fall, but winds any time during the year. Even during the stormy winter season when powerful storms can cross the region.
At low-levels, the situation was more mixed. For example, at Napa Valley Airport (36 ft), the sustained winds at 11:15 PM October 9 (37 knots) were the strongest observed (looking back to 2001) at that location from July 1- November 30, while at the Santa Rosa Airport (KSTS) the sustained winds only reached 28 mph, with 40 mph gusts.
So why were the winds so strong and unprecedented at higher levels in the hills? These winds were key for causing the wildfires to explode and to quickly move into populated regions. And the winds undoubtedly damaged power transmission lines and thus helped start electrical fires, which may, in fact, have initiated the big wildfire runs. And why were the lower-level winds less severe? What can explain such differences?

Read the full story here.

It is worth reiterating straight away that when he talks about “unprecedented”, he is only looking at records going back to 1991.

And, indeed, there was a remarkably similar wildfire in the same area in 1964, known as the Hanly Fire.

The Press Democrat published an article about this in 2013:

Black streaks run 40 feet up the trunks of a ring of redwoods in the Pepperwood Preserve off Porter Creek Road in the Mayacmas Mountains northeast of Santa Rosa.

The trees are healthy, silently bearing the scars of the epic wildfire of September 1964 that rattled Santa Rosa’s nerves before it was stopped about 100 feet from the door of the old Community Hospital on Chanate Road.

Nearly all of the 3,200-acre preserve was scorched as 70 mph winds, close to hurricane strength, blasted the Hanly fire from Calistoga through Knights Valley, Franz Valley and down the Mark West Canyon to what was then the northeast outskirts of Santa Rosa.

At 52,700 acres, the Hanly fire is the largest in Sonoma County — and fourth-largest in the Redwood Empire — in the last half-century.

It pales in comparison to California’s mega-fires, including the 255,560-acre Rim Fire still burning in and around Yosemite National Park, now the state’s third-largest wildfire since the 1930s.

Firefighters and forest ecologists say it’s unlikely the Redwood Empire will ever see such massive blazes, but destructive wildfires regularly erupt in the region, as they do all over the state.

The Hanly fire, ignited when a deer hunter tossed a cigarette into dry grass on the slope of Mount St. Helena in Napa County, remains as testimony to what happens when California’s recreation-friendly Mediterranean climate bakes grass, brush and trees dry every summer.

"All it needs is an ignition source," said Michael Gillogly, the Pepperwood Preserve manager, standing on an east-facing slope that the Hanly fire’s flames raced up 49 years ago. "It could burn any time."

Firefighters and forest ecologists agree: About 4,400 wildfires a year, covering nearly 220,000 acres, according to a recent five-year average reported by Cal Fire, are part of the circle of life and death in California.

"Fire is another of those processes built into the landscape," said Rick Mowery, a Mendocino National Forest fire ecologist. "A lot of California relies on fire to function in a healthy way."

Over thousands of years, the state’s flora and fauna have adjusted to fire, Mowery said. Species that couldn’t tolerate it "were gone long ago."

Nobcone pines can’t propagate without fire, while Ponderosa pines and redwoods are cloaked in thick bark that insulates them from all but the hottest fires.

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The big difference between then and now is that many more people live in places like Santa Rosa. According to Wikipedia, the population there has exploded from 31000 in 1960, to an estimated 175000 now.

And Wikipedia also has this account of the Hanly Fire, and how it compares with the recent Tubbs one:

In 1964, the Hanly Fire, the largest fire in Sonoma County history, burned 52,700 acres, with striking similarities to the Tubbs Fire. Since 1964, hundreds of expensive homes, a golf course and clubhouse restaurant, office and medical buildings, light industry, lakeside retirement homes, a long row of nursing facilities, and two hotels were built in the Fountaingrove area, which had been almost entirely open land in 1964.

The path the Hanly Fire took in 1964, as well as the areas it burned, were very similar to the Tubbs Fire: from Calistoga, along Porter Creek and Mark West Springs roads into Sonoma County, burning homes along Mark West Springs and Riebli roads, through Wikiup, and to Mendocino Avenue, where it stopped, across the street from Journey’s End Trailer Park. The fire was propelled by 70 mph winds, close to hurricane strength, moving from Calistoga to Santa Rosa in only about half a day, but it only burned a few dozen homes.

Sonoma County has four "historic wildfire corridors," including the Hanly Fire area. New homes in the fire zones must meet building code requirements for fire-resistant materials for siding, roofing and decks, with protected eaves to keep out windblown embers. But despite a 100-foot fire break that ringed much of the Fountaingrove II subdivision, 600 upscale homes in the same path as the Hanly Fire, virtually the entire subdivision was destroyed by the Tubbs Fire.

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I’ll leave the final comments to the experts who know about these things, from that Press Democrat report:

About 3,500 buildings, including homes for 9,600 people, a school, a PG&E substation and high-tech commercial buildings now occupy the area covered by the Hanly Fire and Nunn’s Canyon Fire in Sonoma Valley. Both started on Sept. 21, 1964 and together burned 65,800 acres and more than 100 homes.

Should the twin fires happen again, the damage to buildings and farms could exceed $1 billion and the firefighting costs would run into the millions, according to a scenario contained in the Sonoma County Hazard Mitigation Plan of 2011.

Current firefighting techniques might curtail the two fires, the scenario suggests, and Hoffmann noted that numerous vineyards now in the Hanly Fire’s path might slow down a blaze over the same terrain today.

But with a strong northeast wind, the phenomenon that drives the area’s worst wildfires, "all bets are off" he said.

Fire fuels quickly recover in burned-over areas. Dry grass can ignite every year; dead and downed forest litter accumulates in six or seven years; brush rebounds in about 20 years.

"California is made to burn," said Marshall Turbeville, a Cal Fire battalion chief based in Sonoma County.

About 33,900 people who live outside the county’s cities — representing 7 percent of the total population — are in areas "potentially at risk of wildland fires," the hazard mitigation plan says.

There are about 12,600 buildings in areas with "high and very high risk of wildfires," with an estimated replacement value of $4.8 billion, the plan says.

The county has four "historic wildfire corridors," including the Hanly Fire area, Sonoma Valley (scene of the Cavedale fires in 1925 and 1966), the Geysers (with fires in 1988, 1999 and 2004 that covered a total of 22,000 acres) and the Guerneville area (hit by major fires in 1923 and 1961, the latter burning 5,800 acres, 18 homes and $500,000 worth of timber.

In Santa Rosa, about one-fourth of the city’s residents live within four moderate, high and very high severity fire zones, mostly hilly, wooded areas all east of Highway 101.

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