Warm and wet monsoon weather propelled northward into the Mother Lode from the Gulf of California is believed to have caused at least six lightning-caused spot fires in Calaveras County Tuesday morning.
When the first of the reported fires occurred at 8:51 a.m., west of Copperopolis near New Melones Reservoir, Cal Fire Battalion Chief Mario Hernandez was supervising the region, said Cal Fire Tuolumne Calaveras Unit Public Information Officer Emily Kilgore.
Limited resources were dispatched to extinguish the spot fire, in accordance with the Lightning Control Plan, which organizes resources to prepare for multiple fire ignitions in a short period of time.
About one hour later, another spot fire was reported near Mountain Ranch on Swiss Ranch Road in a region supervised by Battalion Chief Jared Clinkenbeard.
No fire was located. But then, a flurry of fire reports were issued in the two battalion areas overseen by Clickenbeard on Tuesday.
At 10:03 a.m., there was a spot fire along the North Fork of the Mokelumne River near Glencoe. At 11:02 a.m., a 10 ft. by 10 foot spot burned near Highway 26 and Sky High Drive in Glencoe. At 11:40 a.m., one acre burned at Mountain Ranch Road and Rocky Road near Mountain Ranch.
By afternoon, five acres were burning at Calaveritas Road and Dogtown Road in San Andreas, Kilgore said.
According to the lightning plan, Cal Fire followed a chain of command which effectively allowed the battalion chief to dispatch limited resources in the most effective way possible, Kilgore said. Often times, a single engine may respond to a small spot fire caused by lightning. If they see a large column of black smoke or aggressive fire behavior, they can request additional resources.
“A single engine can handle extinguishing a single tree,” Kilgore said. “If they ask for more, then we send them more.”
The lightning plan also includes keeping staff on shift during the morning hours to assist with firefighting, aircraft reconnaissance flights by Air Attack 440 and the staffing of Blue Mountain Lookout, a fire lookout point located in eastern Calaveras County, she said.
“The lighting plan is working exactly the way it's supposed to work. We don't do this because we’re having a hard time, we do this to manage our resources effectively so we don't encounter having a lack of resources when we need it,” she said.
The fires are caused when combustible materials are struck by an electric jolt. The lighting fires can be caused in any area or environment, but the more dry and dense fuels are, the greater potential for ignition, she said.
The cause of the fire didn’t present a unique danger, she added, but Cal Fire had concerns about the ability to access remote areas, resource management and the populations of threatened areas.
By about 3 p.m., Kilgore said the forward progress of the San Andreas fire was stopped and all others were contained.
It was suspected that all were caused by lightning, she said, but she could not definitively and immediately identify it as the causes.
There were no reported injuries to firefighters or members of the public and no structures were threatened.
Kilgore said Central Calaveras Fire Protection District, West Point Fire Protection District, Altaville-Melones Fire Protection District and the San Andreas Fire Department assisted with fire fighting in their respective regions.
Eric Kurth, a National Weather Service meteorologist, said the monsoon weather pattern was an annual occurrence for the Mother Lode in July and August. It was “less common,” he said, for the lightning and thunder to drift westward from high elevations into the foothills of Calaveras County.
“It's not necessarily producing torrential rains like in India and Southeast Asia, but it does bring moisture, he said. “It's more typical for this monsoon activity to happen in the Sierra, but on occasion it does affect parts of the valley and the foothills.”
Kurth said heating in the southwest, desert region of the United States and Mexico circulated air in a clockwise direction, hurling moist and warm air northward.
The National Weather Service monitored instability in the weather pattern as it moved into San Joaquin County and then into the Mother Lode. They observed what is called, mid-level instability, where heat and moisture present in the atmosphere rises to produce thunderstorms and lightning, he said.
Flashes and ground strikes from the lightning occurred mostly in Calaveras County and Amador County, in locations near Copperopolis, Angels Camp and San Andreas, he said. Flashes were also seen near Oakdale and Waterford and in the Keystone area of western Tuolumne County. Byt the time the storm reached El Dorado County, it had significantly weakened, Kurth said.
The weather pattern brought some limited and widely scattered rainfall, but not enough to be significant, he said.
Most of the precipitation gauged throughout the Mother Lode was around 0.01 to 0.04 inches, he said.
Stanislaus National Forest Public Information Officer Diana Fredlund said no lightning strikes were recorded in the forest on Tuesday and the Mt. Elizabeth area recorded 0.01 inches of rain.
“Lightning is a primary ignition for fires, so we do keep track of that so we make sure we know when they're out there,” Fredlund said. “We’re on the lookout when we know lightning is in the area.”
More monsoon-related thunder and lightning was expected Wednesday afternoon through Thursday afternoon, but farther east toward the crest of the Sierra Nevada mountain range. By Saturday, most of the weather will have shifted east of the mountains, Kurth said.
Temperatures in Sonora were expected to climb into the triple digits by Sunday.
Kilgore said threats of fire ignition were expected through the end of the week.