The formation of a La Niña in the Pacific Ocean could mean warmer and drier weather for Texas in the upcoming months, if history is any guide, says a Texas A&M University expert.

Dr. John Nielsen-Gammon, Texas State Climatologist and Texas A&M University regents professor in the Department of Atmospheric Sciences, said the Climate Prediction Center (CPC) issued a La Niña advisory this month, which means La Niña conditions are in place. A La Niña forms when waters in the tropical Pacific Ocean are much cooler than normal, which can affect weather patterns all over the world, including the southern U.S. It typically means warmer and drier weather that can last for months over much of the country.

“If those conditions last through the end of the year, it will be an official La Niña event,” said Nielsen-Gammon. “Right now, the chances of that happening are about three in four, according to the official forecast.”

One of the strongest ever La Niña events occurred in 2011, which resulted record highs in much of Texas and one of the state’s worst droughts.

Nielsen-Gammon said the latest Climate Prediction Center forecast has the chances of substantially drier than normal conditions for the next several months at around 50 percent, with the chances of substantially wetter than normal conditions closer to 15 percent.

“So dryness is not guaranteed, but it’s a good bet,” he said.

One wild card in the prediction: it appears that this La Niña is a fairly weak one, meaning it could end by spring.

“At this point, it doesn’t look like a super-strong La Niña like we had in 2010-2011. The temperatures in the ocean are not all that much cooler than normal, even down below the surface,” Nielsen-Gammon said. “So the consensus is for a weak to moderate La Niña event. La Niña displaces the jet stream farther north than usual during the wintertime, and this means that Texas tends to see fewer storms and fewer cold fronts, making it likely that the period November through March will be warm and dry. “

He said that in addition to the historical tendencies for La Niña, important forecasting tools are global models that simultaneously simulate the evolution of the atmosphere and ocean. Just about every such model is predicting dry and warm conditions for Texas over the next few months, he noted, and it is rare to find that much consistency among the long-range models.

The Climate prediction Center gives far West Texas almost no chance of being much cooler than normal, he said.

“Texas has been through a drought roller-coaster over the past year. We’re leaving the summer with drought firmly entrenched in parts of West Texas, while most of the rest of the state has decent amounts of moisture even before Tropical Storm Beta’s rainbands arrived,” Nielsen-Gammon said. “For the dry parts of West Texas, though, it means that the soil moisture deficit is unlikely to be remedied for at least several months. This could make for a very hard winter and spring for farmers and ranchers around Lubbock, Midland and the Big Bend area.”

He said it’s too early to say when La Niña conditions will end, but most La Niñas have little effect on late spring and summer rainfall in Texas, “and a few good thunderstorms can end a drought fairly quickly.”

 

By Keith Randall, Texas A&M University Division of Marketing & Communications