Residents see lack of wind, but officials point to complex factors

Grumbling and indignation have been heard coming from the blackedout coastal bluffs of Marin County to the darkened East Bay hills and bucolic Sonoma Valley.

“There is no wind,” the citizens have angrily complained. And yet hundreds of thousands of people in 34 California counties have endured one to two days of preemptive power outages imposed by PG&E because strong winds were forecast.

“That’s days without power so far and more days to come, by all accounts, for no reason we can see,” complained Joe Matazzoni, who lives in Tamalpais Valley, an unincorporated section

of Mill Valley. “There is no wind event. In fact, winds have been much lighter than usual for the past two days.”

Dangerous winds did bloom Wednesday night into Thursday in some higher elevations. There were gusts of 75 mph on Mt. Diablo, 77 mph on Mt. St. Helena and 73 mph on Pine Flat Road in Healdsburg, but Pacific Gas and Electric Co. managers admitted that fireprone Marin County and numerous parts of the North Bay were calm after power was shut off early Wednesday morning.

So why was electricity cut? The answer is complicated, said meteorologists, atmospheric scientists and PG&E officials who relied on National Weather Service forecasts to make the decision.

Sumeet Singh, a vice president in charge of the utility’s community wildfire safety program, said the “complex nature” of the sequence in which PG&E had to turn off power had a lot to do with it.

PG&E created its power shutoff program after the 2017 Wine Country wildfires. The power company was widely criticized for starting most of those fires. The utility then failed to turn off the highvoltage power lines blamed for starting the Camp Fire in Butte County, a disaster that destroyed the town of Paradise and killed 85 people.

Singh confirmed that PG&E this week had shut down some longdistance, highvoltage transmission lines. Because the 70,000squaremile electric system is, in many ways, interconnected, turning off one highvoltage circuit can lead to a cascading effect on customers far away.

The plan, he said, was also to shut down equipment before the winds arrived, not afterward. Still, Singh acknowledged that “we unfortunately also had to impact Marin and some of the additional areas” that suffered shutoffs but experienced little wind.

“It really has to do with the nature of the system itself,” he said.

But that doesn’t explain why the wind forecasts were so unreliable.

The reason lies in the nature of Diablo winds, which are the strong autumn gusts that blow from inland toward the sea during the day and turn the other way at night. These winds are pushed by highpressure systems toward lowpressure areas. The greater the pressure differential, the faster the wind.

The National Weather Service forecast strong Diablo winds this week, but it’s impossible to predict their exact nature, said Janice Coen, a project scientist for the National Center for Atmospheric Research, in Boulder, Colo.

Coen, who has done atmospheric circulation modeling for virtually every major fire in California over the past few years, said winds are hard to predict, especially where the terrain is complex, like in the Bay Area. Temperature differences and even clouds, both of which are difficult to predict, can influence the behavior of winds.

As a result, she said, Diablo winds behave differently from one day to the next depending on atmospheric conditions and whether mountains, buildings or valleys are in the path.

“The models that the weather service uses and the utilities use are good at the timing and location over a few counties at a time,” Coen said. “They produce predictions of regionally strong winds, but what they don’t have now is the ability to be more specific than that.”

The problem, she said, is that there are not enough weather stations close enough together to accurately predict wind behavior or strengths over large distances.

“They are doing the best they can with the weather prediction tools they have and the data they have,” said Coen, who is working on developing more detailed wind models. “I’m hoping we can move to something that is more specific. With more modern tools we can be more confident in what the wind is going to do.

“I think we can do much, much better,” she said.

Wind predictions are becoming more crucial every year, according to climate scientists who say California’s winds could become increasingly problematic during future fire seasons because the state’s annual dry season is getting longer and overlapping the windy months for longer periods.

“Dry fuels persist later into

the winter, when these winds really peak,” said Alexander Gershunov, a research meteorologist at UC San Diego’s Scripps Institution of Oceanography. “If you have a late onset to the wet season, you can have wildfires burning in December.”

San Diego Gas and Electric was the first utility in California to begin public safety power shutoffs after its power lines sparked a series of wildfires in 2007 that charred many homes and hundreds of thousands of acres.

PG&E’s system is modeled after that program, but experts say the desertlike land around San Diego is much flatter and covers a smaller area, making it much easier to predict wind conditions than it is in the rugged, hilly terrain of Northern California.

Michael Wara, the director of energy and climate programs at Stanford University’s Woods Institute for the Environment, estimated it will take at least seven years for PG&E’s system to have enough monitoring capacity to be as effective as the one in San Diego.

“These power shutoffs are going to be with us for a decade,” Wara said, “so we need to start dealing with that reality as a state.”

Red flag warnings continued Thursday in the North Bay mountains, East Bay hills and Santa Cruz Mountains, where the lack of wind continued to frustrate the many residents enduring the outage.

Marin officials said nearly 10,000 households in the county lost power in the outage. By 5 p.m. Thursday, three quarters of those remained without electricity.

Wara’s Marin County home lost power at 2 a.m. Wednesday, and several hours later he said it was a “beautiful, still morning.”

“I’m not saying they shouldn’t turn off the power before it gets dangerous ... (but) there’s a realtime operational component to this that PG&E has not yet mastered,” he said.

Peter Fimrite, Kurtis Alexander and J.D. Morris are San Francisco Chronicle staff writers. Email: pfimrite@sfchronicle.com, kalexander@sfchronicle.com, jd.morris@sfchronicle.com Twitter: @pfimrite, @kurtisalexander, @thejdmorris