Strengthening La Niña worsens longterm forecast
Arizona is in the early stages of its most severe La Niña event since 1988-89, state climate experts said Wednesday.
That means it is likely that the state will be drier and hotter than normal through March, and the trend could continue through July.
"This La Niña seems to be firing on all cylinders," said Gregg Garfin, director of outreach for the Institute for the Study of Planet Earth at the University of Arizona, during an online climate briefing Wednesday. Climatologists expect La Niña to strengthen and persist at least through the spring.
The forecast, coupled with the recent stubborn wildfire near Prescott, have local fire managers concerned.
"It could be a year-round fire season for us," said Curtis Heaton, Prescott National Forest fire management officer.
The 830-acre August Fire south of Prescott was the most serious off-season local wildfire in anyone's memory, Heaton said.
"The resistance to control was just off the charts," Heaton said. Firefighters finally corralled it Sunday after 11 days.
The August Fire was a human-caused fire, and since then forest officials have found numerous abandoned campfires. Heaton urged forest users to put all fires dead out.
Arizona already has been in the grips of a drought since at least 1999, noted Michael Crimmins, a climate science specialist for the University of Arizona's Cooperative Extension Service, during the online briefing.
Prescott's 2007 precipitation by the end of October totaled 71.5 percent, of average at 11.52 inches. As an indicator of the general warmth, its snowfall totaled only 1.9 inches, or 11 percent of the 109-year average at the National Weather Service's official measuring site on the northeast side of the city.
Prescott has not seen any precipitation since Oct. 1, when just 0.03 inches fell. The last rain before that was Sept. 22.
Yavapai County temperatures have been 1 degree to 2 degrees above normal during the past year, and have been especially high in recent days. Several Yavapai County municipalities saw record high temperatures Nov. 8-10, including Bagdad, Sedona, Seligman and Jerome.
The Southwest's weather in October and November is "very quickly exacerbating drought conditions," Crimmins said.
The last strong El Niño event occurred in 1988-89, Garfin said. The current La Niña trend began in mid-August and already has reached the "moderate" strength level of previous El Niño years in 1949-50 and 1970-71.
"Once we get down to this level, these events tend to persist," Garfin said.
The La Niña weather phenomenon produces warmer-than-usual temperatures in the western Pacific Ocean that end up pushing the North
American jet stream farther to the north. It has been streaming across the northern U.S. and southern Canada for several weeks now, producing dry and warm weather in the Southwestern U.S.
Prescott National Forest officials met this week to talk about the climate and worsening wildfire behavior,
"We're actually rethinking the entire fuels program now," Heaton said. Forest officials might need to conduct more large-scale, remote prescribed burns to stave off large wildfires in heavy dead fuels south of Prescott, he said.
They also are wondering how year-round wildfires could affect their budget.
The August Fire - named for a nearby spring - cost more than $1 million to battle. It cost $25,000 just to reopen the Prescott Fire Center's air tanker base, where heavy tankers reloaded nearly 50 times to help stop the August Fire. It remains open.
"We're not designed for winter fire seasons," Heaton said. We're trying to figure out how to deal with that."