Add David Zierden, Florida State Climatologist, to the list of weather experts predicting a continuation of La Niña and dry conditions through winter and at least into spring planting season across the U.S. Cotton Belt.

Zierden, who works from the Florida Climate Center and Center for Ocean-atmospheric Prediction Studies at Florida State University in Tallahassee, opened the 2012 Beltwide Cotton Conferences in Orlando with less than good news about likely weather patterns.

“We had a strong La Niña last spring and summer and also expect it to continue this winter and into planting time,” Zierden said. Ocean water temperature in a specific area of the Pacific Ocean affects global weather patterns. Warmer than usual water in that area creates El Nino conditions and typically wetter and cooler conditions across the Cotton Belt. Cooler water temperatures push thunder storms westward and create drier and warmer conditions for the Southern U.S.

Last year’s La Niña extended further north than usual, Zierden said.

The El Nino/La Niña phenomenon has been tracked and analyzed for decades, and data show strong correlation of drought conditions and La Niña events, he said. “The graphs are not regular and cycles seem to return in two-to-seven year patterns. It’s hard to predict far in advance.” He said under the best conditions predicting a La Niña or El Nino event 9 months to a year out might be possible. A three-month prediction is more likely.

“A La Niña sometimes last as long as three years.” He said analyses of temperature changes in the El Nino/La Niña area from the 1950s show extended La Niña events in the ’50s, again in the mid-70s and into the early part of the last decade.

“La Niña is a trigger for drought,” Zierden said. “And we’re in a La Niña phase now, similar to this time last year.”

He said water temperatures in the Pacific in late December, 2010, and into January, 2011, were about 2 degrees Celsius colder than normal. Temperature got close to normal last summer but cooled off again.

A La Niña phase can cause rainfall patterns to deviate significantly from normal, Zierden said, typically 20 percent to 30 percent less in the Southwest and as much as a 50 percent drop in parts of Florida.

“Last year January through March followed the typical La Niña pattern closely in the Deep South and extended further north than usual. He expects conditions to remain dry through March from the Southeast across to Louisiana and into Texas, New Mexico and Oklahoma.

He said in some years La Niña can bring enhanced rainfall amounts to South Georgia and Florida, “but not last year.”

Last year, drought conditions in the Southeast were more severe than expected, and the Southwest experienced record drought, “especially in West Texas and New Mexico.”

Chances for severe drought may not be quite as strong for the Southeast in 2012, he said. Drought tendencies for the Southwest are “very much enhanced for this spring.”

Cycles offer predictability

Zierden said predicting weather based on El Nino/ La Niña is not 100 percent, “but the cycles give us some predictability.”

He also discussed the effects La Niña and El Nino have on crop yields, primarily in the Southeast. For corn, yields may drag more in El Nino phases than La Niña, he said. Wet winters may mean delayed planting and slow starts.

“Most corn (in the Southeast) is irrigated and with La Niña and a dry, warmer than usual winter farmers may plant earlier and then warmer temperatures during the growing season help the crop thrive,” he said.

With cotton, yield effect is “more of a mixed bag.” He said cotton planting dates are more variable and that more farmers plant dryland cotton. “It’s even more of a mixed bag in an El Nino phase.”

Knowing—or having a good idea—what the weather will be for a growing season might be good information to have but how can that help a producer? Maybe not, but adapting production strategies could give producers a better opportunity in some years, Zierden said.

Computer models that incorporate production data such as soil type, planting dates, crop history and historical weather patterns may help. Those models have shown that planting cotton early when La Niña is expected could be an advantage.

“Planting early following a dry winter, assuming some rainfall, improves the odds,” Zierden said. “It doesn’t work every time. Sometimes the climate pattern will go the other way, but the models at least provide a better chance of making yield. It gives us some predictability.”

He said farmers can get more information on computer crop simulation from agroclimate.org and then can work with Extension agents or other crop consultants to refine production strategies.