San Diego County Seeks|Relief from Weather Gods

SAN DIEGO (CN) – Thousands of people remained under evacuation orders in San Diego County on Friday, and spot fires erupted, but as Santa Ana winds reversed direction and temperatures cooled from 100 to 90, fire officials hoped to control the fires that ravaged the dry hillsides.
     The most dangerous fire, the Cocos Fire in the hills of San Marcos, was 10 percent to 30 percent contained early Friday afternoon, after the shifting Santa Ana winds blew it in two directions Thursday. More than 25,000 homes were ordered to be evacuated by Thursday, but officials let 3,000 homeowners return Friday morning.
     San Marcos public schools, which canceled classes, said school would resume Monday. But Cal State San Marcos remains under an evacuation order. The Cocos Fire has burned down from the hills to the border of the Cal State campus.
     More than 1,000 firefighters from city, county and state agencies have been fighting the Cocos Fire alone, one of more than a dozen that torched the hillsides of North San Diego County this week.
     One death has been reported, apparently a homeless man, in the Poinsettia Fire in Carlsbad, though it’s not clear whether the fire killed him.
     Until the Cocos Fire flared up Thursday, the Poinsettia Fire caused most concern. It burned 400 acres in Carlsbad, a city of 99,000. The Poinsettia Fire was 90 to 100 percent contained by Friday afternoon.
     A wildfire is considered contained when firefighters have dug a fire a line around it – scraped off vegetation down to mineral soil. After containment, firefighters mop up, extinguishing the hot spots inside the contained zone.
     Spot fires, which continued to flare up Friday, are caused by sparks that fly up from fires and settle to earth elsewhere.
     The Poinsettia Fire destroyed an 18-unit apartment complex and damaged another one. It destroyed at least three homes.
     Roads in Carlsbad have been reopened and people allowed to return. The damages from that fire are estimated at more than $20 million.
     Residents in parts of San Marcos (pop. 81,000) and Escondido (pop. 140,000) remained under evacuation orders Friday afternoon, and workers at Palomar Hospital in Escondido were told to “shelter in place.” The hospital was open Friday afternoon.
     At least three new brush fires flared up Friday, and were attacked by fire crews.
     Three fires, or more, burned more than 14,000 acres on Camp Pendleton, a sprawling coastal Marine base, and the adjoining Naval Weapons Station Fallbrook.
     The 380-acre Highway Fire, in Fallbrook, a forested community of avocado groves, was 100 percent contained.
     The National Weather Service predicted cooler temperatures for the region, which should help. Two weeks ago, several days of hot Santa Ana winds off the desert dried out the hillsides, and this week’s Santa Anas blew the hillsides into firestorms.
     Wildfires can create their own weather, sucking air into themselves and blasting it upward. Large wildfires can create their own lightning.
     Santa Ana winds reverse the normal west-to-east airflow over Southern California. High pressure over the Mojave Desert reverses the airflow. Adiabatic heating can increase temperatures so quickly that the wind itself can almost set trees ablaze.
     In adiabatic heating, the tremendous columns of hot air over the desert are compressed as they are blown over the mountain passes. Sucked westward by the cooler air over the ocean and coastal ranges, the hot air sinks and compresses over the mountain passes. This compression can increase air temperature dramatically in seconds.
     To the north of San Diego County, Riverside County, which has so far been spared from this round of wildfires, filled up with smoke Friday, as the normal coastal airflow blew the smoke and ashes northward. The Santa Ana Mountains, still green despite three years of drought, were a smoky bluegray from half a mile away, the air stung one’s eyes, and ashes drifted down over the houses.

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