AUBURN, Ala.—The changing weather patterns that created Alabama’s drought have their origins in the El Nino/La Nina climate cycles.
What to Expect in a La Nina Year
Alabama Cooperative Extension System Precision Agriculture Specialist Dr. Brenda Ortiz explains that current observations indicate a La Nina pattern may be developing. The La Nina (Spanish for “little girl”) phase is characterized by unusually cold waters across the east-central equatorial Pacific.
La Nina effects on the global climate tend to be opposite of El Nino, although this is only a general rule.
During a La Nina event, sea-surface temperatures are generally 4 to 6 degrees Fahrenheit below average between the International Dateline and the west coast of South America.
In the southeastern U.S. this phase is linked to warmer and drier-than-normal conditions during the winter and spring months. During La Nina, storms move up the Mississippi Valley and Ohio Valley, which means that northern Alabama and northern Georgia may get more rainfall than normal while the rest of the Southeast remains warm and dry. This varies between individual events.
A La Nina phase can last as long as two to three years. The longer La Nina events have set the stage for some of the most severe historic droughts in the Southeast. The most recent three-year La Nina phase was 1999-2001. La Nina is also linked with a very active Atlantic hurricane season.
El Nino in the Southeast
In an El Nino (or Christ Child) phase, warmest water temperatures are usually seen around Christmas, giving El Nino its name.
Warm ocean waters cause increases in tropical rain and thunderstorms above the warm pool. These specific oceanic/atmospheric changes are linked to higher than normal air pressure near Indonesia and the western Pacific and lower than average air pressure in the eastern Pacific.
“El Nino does not have the same effect in all parts of the Southeast,” Ortiz said. “When the El Nino phase is in place, storms tend to track along the Gulf Coast and the peninsula of Florida.”
With that track, southern Alabama and southern Georgia could expect to see more rainfall than normal, more frequent storms and up to twice the normal rainfall totals compared with the central and northern parts of the state.
The ENSO phase is also linked with a greater likelihood of severe tornadoes in the South and fewer Atlantic hurricanes. The most recent strong El Nino episode was 2015-2016.
Growers have long been aware of seasonal changes in rainfall and temperature especially as it affects crop production.
Producers experienced this climate variability first-hand during an unusually cool, wet 2016 planting season followed by the state’s most prominent drought in a decade. Now producers may be on track to experience an unusually warm, dry spring as climate patterns point toward a La Nina year.
Ortiz said until recently, growers have only been able to react to these variations, but that is changing.
“For the past three decades, climatologists and crop experts have been working together to revise our understanding of how variations in climate affect growers’ crop prospects and their yields,” she said.
These new insights are changing the face of farming. In crop management terms, what they’ve learned and shared about variability is every bit as important to a grower’s success as fertilization, weed and insect control.
Though several inches of rain fell throughout the state in the last few days of November, the rain map from the past 90 days is the same as the updated maps from the past week. Rainfall in the past few days is all that has been received in nearly three months.
Even with rain in the near forecast, the state is still more than 12 inches behind normal rainfall levels. River flow has already peaked and is beginning to drop again. Over all, the weather pattern indicates the possibility of less rain than normal into the spring.
In order to recover, the state will need as much as two inches of rain each week for a month to begin catching up.
Extension’s Climate and Crops iBook
Learn more about the impact of climate cycles on agriculture in Climate and Crops, Alabama Extension’s newest iBook, at http://www.aces.edu/climateandcrops.
Climate and Crops focuses on the Southeast’s five major row crops: corn, cotton, peanut, soybean and wheat. It features multiple interactive options, including 17 videos, 33 interactive graphics and hundreds of images related to problematic insects, diseases and weeds.
Climate and Crops is a comprehensive resource for farmers, crop consultants, agribusiness and educators.