Low level of precipitation plays role in wildfire risk - The Explorer: News

Low level of precipitation plays role in wildfire risk

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Posted: Wednesday, May 4, 2011 3:00 am

Last week, the U.S. Forest Service and the National Interagency Fire Center (NIFC) warned that the threat for wildland fires in Southern Arizona is very high this year. Their prediction proved true and quite timely as two wildland fires are now blazing south of Tucson.

By Monday, fire had spread to nearly 10,000 acres in the Bull Fire near Nogales, at the Arizona-Mexico border, while more than 1,800 acres were burning in the Greaterville Fire near Sonoita.

At a press conference held last week, Kristy Lund, acting fire management officer for the Coronado National Forest, said the warning had been issued in part because of the low amount of precipitation during the past winter, dry and overgrown vegetation, and warm temperatures.

Lund pointed out the primary factors influencing the wildland fire outlook for the region include La Niña, the weather phenomenon associated with cooler than normal water temperatures in the equatorial Pacific Ocean, which typically means less precipitation and drier conditions in the Southwest.

Drought conditions that have persisted across the Southwest also play a role in the wildland fire potential, as well as the dryness of fuels found in both desert and mountainous areas, she added.

Fuel dryness is classified as moist, dry or very dry.

“We had a very warm and dry winter, and expected a lot of wind events into the spring, which we got,” Lund said. “Tied in with the La Niña pattern, that means potentially very dry conditions, especially because we expect wind events for longer periods, causing it to be hot and dry.”

A wildland fire is a non-structure fire that occurs in the wildland, both unplanned ignitions and prescribed fires. Prescribed fires are those purposefully ignited in wildlands to reduce wildfire risk, improve forest health or rangeland vegetation.

Wildland fire conditions usually worsen when red flag warnings are posted, said Heidi Schewel, public information officer for Coronado National Forest.

“Red flag warnings are triggered by a combination of wind, low relative humidity and temperature,” she noted, and not a specific wind velocity.

Once a wildland fire is ignited, it might be handled in several different ways, Schewel said. Changes in fuels, weather, topography, governmental jurisdiction and public tolerance all play roles in whether and how a wildland fire may be fought.

Lund noted that the fire managers use a decision support process to guide them.

“The process assesses the situation, analyzes the hazards and risk, defines implementation actions and documents decisions and their rationale.

Resources at the disposal of fire managers include initial attack resources, Type 1 crews, Incident Management Teams, and Type 2 and Type 3 teams.

NIFC records show that one of the worst years for wildfire destruction, 2000, had nearly 3 million acres of land destroyed and pushed the cost of fighting the wildfires to $1,362,367.

Dugger Hughes, special operations chief for Northwest Fire District and a national Type 1 Incident Commander, offered guidelines for protecting oneself and one’s property from wildland fires.

“Make sure your home is defensible in terms of fire,” Hughes said. “Clear out any combustibles for 30 feet around your home — the dead leaves, grasses and branches, not the live bushes. If fire encroaches on your home, that space allows firefighters to get in there and safely work to save your house.”

Residents also should think about where they would go in case a wildland fire threatens their home.

“You already should have planned what you’ll take with you, and where you would have to drive or evacuate,” Hughes pointed out.

He said the deserts in the Southwest have extremely dry fuels, but not a lot of grasses because we didn’t experience a lot of winter rains.

“However, there’s a dead aerial component in the deserts from the several hard freezes that we had during the winter and that now would add to critical fire behavior,” Hughes said. “It’s something to consider.”

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