The El Niño-La Niña cycle has been linked to weather patterns for a long time. Sometimes it’s associated with blocking weather fronts and producing droughts. Other times, it’s associated with wet years.
The cycle refers to sea surface temperatures off the coast of the Pacific Ocean. When the temperature of the ocean surface waters is above normal, it usually ties to an El Niño event. When the temperature is below normal, it triggers a La Niña phase. The period in between is the “neutral phase,” weather experts say.
Ocean temperatures over vast areas are important because they can influence barometric pressure, and thus impact air circulation patterns aloft. This influence can be felt worldwide. Climatologists say cycles are irregular — there’s no set amount of time for the cycle to be in any one phase.
One of the first times the El Niño-La Niña cycle was discussed in the farm press was in 1983, when the cycle played a role in blocking weather fronts and producing a midsummer drought across the Midwest, including Indiana. The late Jim Newman, a Purdue University agronomist and climatologist by trade, helped farmers understand why their cornfields were burning up that year.
Beth Hall, who recently became the Indiana state climatologist and who is based at Purdue, explains that currently, a weak El Niño persists.
“The El Niño which has been ongoing for a while is still present and relatively weak,” she says. “It is expected to continue through summer 2019. There is a 70% chance it will continue. However, it’s expected to weaken on through fall.”
Hall bases her information on data reported by the National Oceanic and Atmospheric Administration’s Climate Precipitation Center. Read the report here.
Historically, an El Niño has been associated with above-average precipitation, particularly in May and July, she notes. However, Hall was unable to find any statistical significance between La Niña-El Niño years and corn yields.