- Most of Texas remains in the worst drought category, D-4.
- Conditions could persist into 2012, or longer.
- La Nina is to blame.
He doesn’t predict with certainty that the current drought will persist into 2012, but he says current models indicate the chances are greater that conditions will remain dry than that they will moderate.
He refers to various computer models that “predict cooler temperatures in the Pacific” favoring continuation of La Nina and dry and warm conditions across the Southern United States.
He showed a graph with a bar divided into four possibilities: driest in 30 years; tenth driest in 30 years; tenth wettest in 30 years; and wettest in 30 years. Under typical circumstance, the two extremes would have about a 33 percent chance of occurring and the middle position also 33 percent. But with current projections, Nielsen-Gammons said the bar tilts toward warm and dry. “We see about a 40 percent chance that Texas will be in a drought period through fall and early winter,” he said. He sees only a 27 percent chance that conditions will be wetter than usual.
He said the state had a “reasonable chance” of rainfall for the next two weeks—a prediction that was borne out in some areas of the state from October 7 through 12. “That reasonable chance will be available,” he said, “until we get locked into La Nina.”
He also noted that even with a 3-inch rainfall, areas like Lubbock will “still be below average rainfall.” Folks who take advantage of showers to plant wheat have to consider the possibility of getting enough moisture to “get through the winter,” he said.
Unfortunately, conditions may not get much better any time soon.
“Texas rainfall has been increasing over the long term,” Nielsen-Gammon said. “But it’s been erratic. The extreme far west has been about the same for 100 years. The rest of the state has seen about a 10 percent increase over the last century, so rainfall average is relatively flat and nothing to worry about as far as climate change and rainfall, at this point.”
He said since 2000 Texas rainfall has included a series of wet years interspersed with drought.
Natural changes, he said, hold the key. In addition to the La Nina/El Nino effect, the Atlantic Ocean also affects Southwest weather. “In the 1950s, warm Atlantic waters and cold Pacific waters created the 1950’s drought period that persisted into the 1960s. That’s the only time those conditions have overlapped.”
Until now, perhaps. “We’ve had a warm Atlantic since 1995 with a lot of hurricane activity.”
Based on potential for La Nina and other factors, “it looks like a two-year drought at a minimum. But it’s hard to predict. If we’re lucky, we’ll have only two years of drought, but we look at the ’50s and know that long droughts are possible. Sooner or later we will see something worse than the 1950’s droughts.”
He said the chance of a five-year drought is about one in four “maybe a little less than that.”
Ocean temperature oscillations, he said, have been occurring for thousands of years. “But our ability to forecast has improved. We’re just beginning to have computer power and computer models to forecast on a large scale. In the future, we will probably be able to make more accurate ocean forecasts and more long-term predictions.”
He said some factors can’t be predicted, however. Sun spots and volcanoes may reduce temperatures. “We’re in a period now with less solar activity, and fewer sun spots.”
He said global temperatures have increased over the last century and “carbon dioxide is causing climate change.”
Nielsen-Gammon said the 2011 drought extended from Texas west into Arizona, north into Kansas and eastward to Georgia and South Carolina.