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Combination of Rain, Dry Spells Turns Landscape Into a Tinderbox

October 16, 1985|SCOTT HARRIS | Times Staff Writer

When the California Department of Forestry circulated its fortnightly fire hazard forecast Oct. 2, it predicted "intermittent periods of thunderstorms and higher humidities" for Southern California from Oct. 9-15. And temperatures were supposed to fall below normal from Oct. 12-15.

"Well," said National Weather Service forecaster Nancy Dean as she reviewed the state report on Tuesday, "you can't be right all the time."

As anyone with chapped lips and a parched throat can attest, Southern California was instead visited by the hot, dry Santa Ana winds--ideal conditions for a brush fire.

The Santa Anas came at a time when the region was primed for major fires. A rainy 1983, followed by relatively dry 1984 and 1985, have helped cover the outlying mountains, hills and valleys with thick but dry vegetation--chaparral that acts like tinder to the approaching flames, fire authorities say.

And although the two-week forecast was off the mark, forecasters on Sunday accurately predicted that Santa Anas would blow in over and through the mountains from Nevada, enabling firefighters to prepare for a "red flag" alert.

Still, there was often little that could be done in the face of adverse weather conditions, authorities said.

Up to Mother Nature

"You really have a difficult time trying to extinguish a brush fire until Mother Nature lets you," said Vince Marzo, spokesman for the Los Angeles Fire Department.

Officials with the forestry, fire and weather agencies go back to 1983 to explain why Southern California was ready for another rash of brush fires. That was a very wet year, with 34.04 inches of rain falling at the Civic Center, compared to the average of 14.85 inches.

The head deputy forester for Los Angeles County, Bob Johnson, said that the rain fed a lush growth of brush, particularly the ceanothus--a family of native plant species that includes buckthorn, wild mountain lilac and some wildflowers. But a pair of dry years--8.9 inches of rain in 1984 and 5.26 inches so far this year--have weakened and killed the ceanothus.

What is usually a moist, fire-resistant plant has become tinder-dry, Johnson said. "Chaparral always burns. Ceanothus usually slows the fire."

Aware that the Santa Ana conditions were imminent, the county Fire Department issued a red flag warning Monday morning, posting extra firefighters and engine companies in outlying areas that posed great fire risk. The city Fire Department issued a red flag alert on Monday afternoon.

Conditions for Alert

The county issues the alert when humidity is below 20%, winds are above 25 m.p.h. and the "fuel heat/moisture index"--a means of measuring the combustibility of the brush--is above a ranking of 85. The Santa Anas can quickly dry vegetation, making it more highly flammable. (The city Fire Department calls a red alert when the humidity falls below 15%.)

The likelihood of fire is enhanced by the region's distinct wet and dry seasons. More than 14 inches of rain falls on average from November through April and less than an inch from May through October.

"All the vegetation grows so lushly, then it dries out. It happens every year," said Peter Wilensky, a weather service meteorologist.

As a result, fire "is an annual problem we have to deal with. It's a very natural part of our environment," he said. "The problem is that we (are) building in places that are likely to burn."


30-year average 14.85 inches 1983 34.04 inches 1984 8.90 inches 1985 to date 5.26 inches 1985 estimate 9.00 inches

National Weather Service figures from the Los Angeles Civic Center. FIRE AREAS AT A GLANCE 1. Ferndale/Wheeler Canyon, 65 miles northwest of downtown Los Angeles and a few miles from Ojai. 35,000 acres. Started 9:30 p.m. Monday. Out of control. Loss: Eight homes, five mobile homes and more than 20 other structures.

2. Peach Hill, between Moorpark and Camarillo, 45 miles northwest of downtown Los Angeles. Started 3:40 p.m. Monday. 1,000 acres. 20% contained. Arson suspected.

3. Fillmore, in Ventura County, about 50 miles northwest of downtown Los Angeles. 500 acres. 95% contained.

4. Moorpark, in Ventura County, 40 miles northwest of downtown Los Angeles. 300 acres. Started 3:30 p.m. Monday. Out of control.

5. Tapo Canyon, in Ventura County, 35 miles northwest of downtown Los Angeles. 10,000 acres. Started mid-afternoon Monday. 25% contained. Arson suspected.

6. Pioneer or Hummingbird Ranch, in Ventura County, about 40 miles northwest of downtown Los Angeles. 1,600 acres. 25% contained. Caused by car accident.

7. Box Canyon-Pioneer Canyon, 30 miles northwest of downtown Los Angeles on the Los Angeles-Ventura County line. 1,600 acres. Started noon Monday. Reported 100% contained. Loss: one house, one heart attack victim.

8. Decker Canyon, stretching down to the ocean, 40 miles west of downtown Los Angeles. 5,800 acres. Started noon Monday. Loss: four houses and a garage. Out of control. Arson suspected.

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