El Nino Pulls a Disappearing Act, So Our Winter Should Be Warm, Dry
Davis, Tony, AZ Daily Star
Call it the El Nino that isn't.
And expect an especially dry, warm winter in Tucson as a result.
Over the summer, the eastern tropical Pacific Ocean temperatures near the international date line were about 1.2 degrees warmer than normal. More often than not, such warming is a sign that an El Nino winter season bringing wetter-than-normal and cool weather is headed our way.
Federal weather forecasters at the time foresaw a 70 percent chance of an El Nino-dominated winter of 2012-13 in the Tucson area and across the Southwest.
But in a rare event in September that remains unexplained, the predicted El Nino conditions never occurred. The forecast dissipated.
In its place has come a long-term forecast for a winter much like the past two: below-average rainfall and above-average temperatures for at least most of the upcoming winter.
Forecasters are predicting dry weather not just in the Tucson area, but also, tentatively at this point, up in the Upper Colorado River Basin in Wyoming, Utah and Colorado. There - the source of much of Tucson's drinking water supply through the Central Arizona Project -snowpack is currently 50 percent of normal.
While some snow is expected there in the next two weeks, it's overall "just not looking good," said Klaus Walter, a University of Colorado research associate.
"These things happen. There's not really much to say about it. It was a weak El Nino event when it started, and it dissipated," said Walter, who specializes in diagnosing El Ninos and other winter weather patterns. But, he added, "I would give the El Nino a 5 percent chance of reviving. It's not completely off the table."
Drought has been the norm in our area for years now. In the past six years, most of the Southwest has received between 71 and 90 percent of average precipitation, said the University of Arizona's Climate Assessment for the Southwest. About 99 percent of the state is in at least moderate drought as of Nov. 13, the assessment said. The most severe conditions are in the Four Corners area near the New Mexico border.
Nearly 80 percent of Pima County has been at a severe drought level most of this year, although western Pima County was in a moderate drought, said a memo released this week by County Administrator Chuck Huckelberry, citing reports from the U.S. government's drought monitor.
This year's rainfall in Tucson of 6.73 inches has been nearly 4 inches below normal. Last winter's 0.56 of an inch from January through March was barely one-fifth of normal, says the county's Local Drought Impact Group, which consists of water agencies and other local, state and federal agencies in this area.
The last two winters and four of the past six have been La Nina winters, which typically are warm and dry in the Southwest.
But this summer, with the warmer Pacific Ocean temperatures, a "pretty strong consensus" existed among weather forecasters that we were heading into an El Nino period, said Michelle L'Heureux, head of the El Nino-La Nina forecasting team for the National Oceanic and Atmospheric Administration. …