LOS ANGELES Oct 30 (Reuters) - Fast-moving Santa Ana winds are expected to blast through Southern California on Wednesday, whipping up new wildfires after a brief respite for firefighters on Tuesday.
The National Weather Service (NWS) issued a rare "extreme red flag" warning for wildfires.
"I don't know if I've ever seen us use this warning," said NWS forecaster Marc Chenard. "It's pretty bad."
The Santa Ana winds blowing westward off the desert and mountains into Los Angeles and Orange County are expected to reach sustained speeds of 50-to-70 mph Wednesday and into Thursday, Chenard said.
Firefighters got ready to do battle again after a day of light breezes that helped them gain ground against a blaze displacing thousands of Los Angeles residents near the Getty Center museum. Strike teams and equipment were posted on standy at strategic points throughout the state.
City arson investigators said on Tuesday the Getty fire was likely to have been caused by a broken tree branch being blown into power lines during high winds on Monday morning.
Electricity remained cut off to roughly half a million homes and businesses in northern and central California on Tuesday as a precaution by the state's largest utility.
The NWS's Storm Prediction Center said that a critical or extreme fire danger existed for more than 34,000 square miles of California, encompassing some 21 million people.
Governor Gavin Newsom, who has accused utilities of failing to adequately modernize and safely maintain their power systems, paid a visit to the Getty fire zone on Tuesday afternoon.
"This is a challenging time," Newsom told reporters at a command center in the University of California's Los Angeles campus.
At the start of the day, firefighters in Los Angeles and those battling a much larger conflagration in northern California's Sonoma County wine country took advantage of lighter winds to make headway before hazardous winds reemerged.
Fire officials worried that high winds forecast to gust to 70 miles (113 km) per hour or more would lift embers from smoldering hot spots and carry them into unburned vegetation, re-igniting and spreading flames anew.
Los Angeles Fire Chief Ralph Terrazas said extremely high winds could also force water-dropping helicopters, a vital component of the firefighting arsenal, to be grounded.
An army of some 1,100 firefighters battled the Getty fire Tuesday in a narrow window of slower winds and consolidated those gains a day after flames and embers spread over scrub-covered slopes around expensive homes on the city's west side.
By early Wednesday, crews had managed to confine the blaze to about 650 acres (263 hectares) while carving solid containment lines around 15% of its perimeter.
In northern California, where firefighters struggled for a sixth day against a 76,000-acre blaze in Sonoma County's wine-making region, high-wind forecasts prompted Pacific Gas and Electric Co to impose a new round of blackouts for nearly 600,000 homes and business.
That included about 400,000 customers blacked out in a power shut-off that PG&E instituted days earlier, the company said.
Early Wednesday, PG&E announced that it had restored about 73 percent of the 970,000 or so customers affected in earlier shutoffs.
Utilities serving Southern California's more highly urbanized areas have imposed smaller-scale outages.
Announcing preliminary findings of its Getty fire investigation, the Los Angeles Fire Department said the blaze probably started when a tree branch snapped off in high winds landed on power lines, producing sparks and "arcing" that ignited nearby brush.
The lines, which are operated by the city's Department of Water and Power (DWP), remained intact, the statement said.
PG&E has been implicated in the Sonoma County blaze, dubbed the Kincade fire. The utility acknowledged last week that the Kincade fire broke out near a damaged PG&E transmission tower at about the time a live high-voltage line carried by that tower malfunctioned.
The company, whose mass power shutdowns have drawn harsh criticism from the governor, filed for bankruptcy in January, citing $30 billion in potential liability from a series of deadly fires sparked by its equipment in 2017 and 2018.
Citing progress made against the Kincade fire, Newsom said the number of evacuees in northern California had diminished from 190,000 at the peak of that blaze to 130,000 on Tuesday.
Property losses from the Kincade, listed at 15% contained, were put at 189 homes and other structures, double Monday's tally.
The size of the Getty fire's evacuation zone was reduced by roughly 3,000 homes on Tuesday but residents of about 7,000 dwellings remained displaced, fire officials said. At least a dozen homes have been destroyed so far. (Reporting by Steve Gorman in Los Angeles; additional reporting by Rollo Ross in Los Angeles and Rich McKay in Atlanta; Editing by Angus MacSwan)