Expected Winds Kindle Fire Fear

With Santa Ana gusts of up to 50 mph forecast for this week, firefighters said Monday that the behavior of last week’s wildfires suggests that they will have their work cut out for them as the fall fire season continues.

To underscore the potential danger, the National Weather Service on Monday issued a red flag warning for fire danger because of high winds and low humidity for most of Ventura County, and parts of Los Angeles, San Bernardino and Riverside counties.

The weather service expects those conditions to continue through Wednesday.

The last major Santa Ana winds hit Southern California on Wednesday, igniting several brush fires including one on the Los Angeles-Ventura County border that burned 24,000 acres and threatened thousands of homes.

Firefighters said Monday that that blaze, known as the Topanga fire, was able to grow so fast because the wind had dramatically reduced humidity and had reached speeds up to 40 mph.

This Monday’s humidity was about 40%. But with Santa Ana winds, the humidity could drop as low as 5% in inland areas and 10% to 15% in areas closer to the ocean. Those conditions further parch dry brush. The winds are worrisome this year because the heavy winter rains produced more, much taller brush and grass than in past years.

“When a fire gets going and we’re under Santa Ana wind conditions, it’s going to go where it wants to go,” said Bob Eisele, a fire behavior analyst who is working on San Bernardino County’s Thurman fire. “The best thing we can do is try to protect structures until it hits some natural barrier that stops it, or until the wind quits.”

According to the weather service, mountain areas in Los Angeles and Ventura counties can expect winds of 20 to 30 mph gusting up to 50 mph and inland mountains can expect winds up to 30 mph.

Humidity in the Topanga fire zone is expected to drop to 10% to 15%, and humidity in the inland mountains is expected to be 20% to 30%.

Eisele worries that the winds could do more damage -- dropping humidity to 3% or lower.

He also is concerned that the winds can carry embers into an unburned area, where there is dead vegetation, and reignite the fire.

“That’s why we intend to stay here and keep a much larger force than we normally would,” Eisele said.

Tim Chavez, a fire behavior analyst at the Thousand Oaks base camp, said officials at the Topanga fire were holding on to some crews that would have been dismissed if there had been no Santa Ana winds forecast.

About 1,000 firefighters, who are combing for latent coals, remain in the burn area, as well as three aircraft that are ready to dump retardant or water on any flare-ups, he said.

“If we can hop on this stuff with a couple of tankers and helicopters and 10 to 15 engines, we can catch almost anything,” he said. “But if it’s in a remote area and aircraft are committed to other fires, that’s when they get away.”

Chavez said the scarcity of air tankers Wednesday was one of the main reasons the Topanga fire went out of control. The hilly topography, months of sun exposure for vegetation and the Santa Ana winds were able to kindle a small fire into an intense blaze.

Firefighters started getting the upper hand on the fire only two days ago, when the wind weakened and night air moistened.

“The wind never quits blowing, but it slowed down enough for us to get around it,” Chavez said.

Officials also are on guard in San Diego County, which in 2003 was the site of the worst wildfire in state history. That fire was also driven by Santa Ana winds.

Pete Scully, a battalion chief with the California Department of Forestry and Fire Protection in San Diego, worries that the next bout of winds will turn the abundant grasses “extra flammable, like flash paper.”

Scully said it was hard to say whether the conditions that started the Cedar fire were worse than the current conditions.

Certainly this year there are more grasses, which always burn first and also provide a path for flames to travel between shrubs.

But there was plenty of brush in 2003 and that brush had less moisture. When water and sap compose less than 65% of a shrub’s weight, it becomes a fire hazard, Scully said. In his area now, chamise, a tough shrub common throughout the state, holds only 54% of its weight in water and sap.

“We’ve got conditions that are ripe for a fast-moving, hot-burning, spotting type of fire,” he said. “We could just as easily have another Cedar fire.”