If you didn’t like the summer of 2011, chances look pretty good that you aren’t going to be happy with 2012, either. And 2013, ’14, and ’15 could add to your discontent.
“This past year we had an unusual drought,” says Texas A&M professor of meteorology and state climatologist Dr. John Nielsen-Gammon. “And we have a strong possibility of it continuing.”
Nielsen-Gammon, speaking at the recent Beef Financial Management Conference in Amarillo, said most of Texas remains in the worst drought category, D-4, with only a few areas “around the edge” in less dire straits.
He said the drought overall is so bad that the current rating system may not be broad enough to cover it. “We might need a D-5 or a D-6 designation,” he said. “And the longer a drought goes on the worse it gets.”
He said average rainfall for the state for the last 6 months was only 5 inches. “We’ve been running from 35 percent to 40 percent of normal rainfall for the past 11 or 12 months.”
The drought of 2011 (It actually dates back to last fall.) ranks as the worst in recorded history for much of Texas, eclipsing 1917, 1934 and 1956. And most of the state recorded drought conditions that would be in the top ten worst droughts in history.
The difference, so far, between the current drought and the infamous 1956 drought, is duration. Worst in history
“In 1956, they were experiencing long-term statewide drought. But 2011 represents the worst short-term drought in Texas history,” Nielsen-Gammon said
Analysts have to go back 100 years to find anything close to 2011. “We’ve had 12 consecutive months with below average rainfall. September was the seventh consecutive driest month on record.”
He said parts of East Texas remain in a drought that has lasted four years. Recent rains have provided a bit of hope that the drought may be ending but consistent rain will be necessary to break the drought. Nielsen-Gammon said some North Texas Counties had rain last May and that far West Texas had recent “monsoon” rains. “But most of the state is still dry. Some pockets have had less than 10 percent of normal rainfall for the past six months. Most of the state has received less than 25 percent of normal rainfall during that time.”
He said intense heat from June through August, “well above what’s been observed before,” added to the problem.
Blame La Nina
La Nina gets most of the blame for the prolonged drought. “For the past 20 years Texas has fit the pattern of La Nina/El Nino,” Nielsen-Gammon said. That pattern shows that when waters in a specific area of the Pacific Ocean are cooler, the Southern United States experiences warm and dry conditions. That’s La Nina. When those waters are warmer, El Nino comes into play and conditions are cool and damp in the Southern United States.
“Most climatologists credit La Nina for the current drought,” he said.
But other factors also contribute to Southwestern weather patterns. Tropical storms in the Gulf of Mexico may break drought cycles as may storms coming across the Sierra Madre.
Nielsen-Gammon said drought contributed to the unusually high temperatures in the Southwest last summer. “Because of dry conditions, we also had high temperatures,” he said. “Most of the excess heat was due to lack of rainfall and lack of evaporation.”
He said evaporation from soil and plants helps cool temperatures. With drought, plant growth is diminished and evaporation reduced. “Solar energy goes into the soil instead of into evaporation, so it gets even drier.”
He said temperatures in Texas have been “unusually warm over the past decade. Except for the Panhandle, Texas’ coolest decade was the 1970s.”
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.