- Fire officials designate wind conditions as "purple" threat for first time ever
- Winds could intensify fires as mandatory evacuations ordered in Ojai Valley
(CNN)Dry weather and merciless winds, with gusts predicted to reach the strength of a Category 1 hurricane in mountainous areas, threaten to intensify the already devastating Southern California wildfires that have driven 110,000 people from their homes.
Hundreds of firefighters have been working nonstop to battle the blazes racing across hillsides and through neighborhoods. Almost 9,000 homes are without power. Officials have shut down schools and closed major thoroughfares.
Despite a brief respite in the winds Wednesday, they began picking up again in the evening. A gust of 85 mph was detected in Ventura County. Forecasters say Thursday will bring gusts of 80 mph in the higher altitudes, while winds of 50 to 70 mph will make firefighters' mission extremely difficult in Ventura and Los Angeles counties.
The humidity won't help. It will still be low Thursday, meaning the trees and brush fueling the fires will continue to be tinder.
"We stand a fairly good chance of a very challenging night and day (Thursday)," said Tim Chavez, a fire behavior analyst for the California Department of Forestry and Fire Protection, or Cal Fire, at a news conference on the 96,000-acre Thomas Fire in Ventura County. "There's a lot of potential for some large fire growth."
The Thomas Fire was 5% contained as of early Thursday. The fire is roughly the size of Denver.
Officials say they will see a "recipe for explosive fire growth" and an unprecedented fire danger score. According to the Los Angeles Fire Department, experts grade fire danger by measuring the moisture in dead vegetation, the temperature, wind speed and direction, and then assessing historical weather information.
A value of 48 is considered high danger, while 162 is extreme. Thursday's score: 296, a record.
It's not the only first that firefighters have experienced with the Southern California blazes. The scale used to measure the potency of the Santa Ana winds typically runs from gray, for little or no danger, to red, for high danger.
"The forecast for (Thursday) is purple," said Ken Pimlott, director at Cal Fire, according to CNN affiliate KCBS. "We've never used purple before."
• More evacuations: Several cities in the Ojai Valley are under mandatory evacuation. Satellite images by the National Weather Service showed the city of Ojai surrounded by fires.
• Areas of concern: Firefighters said they are keeping the Skirball Fire at bay but worry it will jump west of Interstate 405.
• School closures: More than 260 Los Angeles public and charter schools will be closed Thursday and Friday.
• Out-of-state help: About 300 engines are coming from fire departments in other states, Los Angeles County Fire Department Chief Daryl Osby said.
Stretching 140 square miles
The Thomas Fire in Ventura County, which sits just north and west of Los Angeles, grew significantly Wednesday to about 140 square miles.
Officials said they couldn't give a precise number of homes destroyed, because flames in burned neighborhoods still were too intense for examination. But they had estimated about 150 buildings as of Wednesday night. The number will increase once the focus shifts from firefighting and rescue to more damage assessment, fire officials said.
Airborne embers were irritating firefighters' eyes, said Rich Macklin, a Ventura County fire spokesman.
California Gov. Jerry Brown has declared an emergency for the county, freeing state resources such as the National Guard to support response efforts.
The 475-acre Skirball Fire near the tony Bel-Air area of Los Angeles startled commuters Wednesday morning on I-405.
The busy freeway was shut down over a 9-mile stretch for hours as the fire got closer.
"It was dark until I saw a gigantic ball of orange," motorist Tiffany Lynette Anderson wrote on Instagram, where she posted a picture of fire raging beside the highway before it was closed.
"I could feel the heat on my windows," said Los Angeleno Joy Newcomb, who also drove by the fire.
The freeway has since reopened, but some ramps remained closed.
Firefighters worked Wednesday night to keep the fire from jumping west of 405 and to battle some flare-ups, said Peter Sanders, a spokesman for the Los Angeles Fire Department.
Los Angeles authorities ordered parts of the Bel-Air district near the fire to leave, but those are just a fraction of the evacuations that have been ordered in Southern California since Monday night.
Smoke collected even in areas that weren't burning. Health officials warned people in the heavily populated San Fernando Valley and other parts of the northern Los Angeles area to limit their time outdoors.
A video posted to Instagram shows a Los Angeles County Fire helicopter maneuvering around heavy smoke to make a water drop on the Skirball Fire.
The smoke from the fires could be seen from the International Space Station. Astronaut Randy Bresnik wrote in one tweet: "I was asked this evening if we can see the SoCal fires from space. Yes Faith, unfortunately we can. May the Santa Ana's die down soon. #Californiawildfire."
CNN's Carma Hassan, Cheri Mossburg, Jason Hanna, Madison Park, Stella Chan and Steve Almasy contributed to this report.