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Rocky Fire Unpredictable For Firefighters

Jeff Chiu / AP

A firefighter sprays a hose toward a spot fire in the Rocky Fire burn area along Morgan Valley Road near Lower Lake, Calif., Friday, July 31, 2015.

Jeff Chiu / AP

The Rocky Fire burned in an area dominated by chaparral vegetation. Regional ecologist Hugh Safford with the U.S. Forest Service says when that catches fire, it’s often unstoppable.

“It’s behaves explosively, it’s an extremely flammable vegetation type particularly after a lot of years of drought," says Safford. "My guess is that there was probably quite a bit of dead fuel in the chaparral out there. When that stuff burns it’s just going to be big and it’s better that people aren’t around it.”

Energy from the combustion of fuel can create a giant column or plume of fire. 

“The column itself is rising because of convective heat and as a result it’s pulling air in from the surrounding areas," says Brandon Collins, a fire ecologist with the U.S. Forest Service Pacific Southwest Research Station. "That in itself can create winds from multiple directions.”

Collins says when that plume collapses, called a downburst, it also sends wind in different directions making the fire completely unpredictable and defying most computer models. But Collins says this kind of fire behavior is happening more often. It also happened during the 2013 Rim Fire outside of Yosemite National Park and last year during the 97,000 acre King Fire in Placer County.

“It’s hard to draw a trend line through three years and three extreme events, but it just seems like its happening a little more frequently than it has in the past when they were spread out by several years as opposed to back to back to back,” says Collins.

Chaparral vegetation historically would only catch fire once every 60 years. But it needs fire to sprout and grow. Ecologists say as a result, the vegetation in the burn area of the Rocky Fire will probably grow back quickly.