Cooling in the Pacific Ocean over the past several months has led to the development of La Niña, which is likely to be classified as a moderate or strong event this winter, says a meteorologist for MDA EarthSat/CropCAST.

A moderate or strong La Niña typically produces a drier-than-normal weather pattern across the southern U.S., including much of the winter wheat belt in the plains. This dryness can have a negative impact on winter wheat yields, as it most often occurs during the two critical development periods.

The first is the germination and establishment period during fall. "Since mid-September of this year, a pattern similar to previous moderate/strong La Niña years has evolved, with dryness occurring across eastern Colorado, western Kansas, Oklahoma and Texas,” says meteorologist Kyle Tapley. “The dry weather has stressed germination of the wheat crop and may lead to poor establishment."

Following moderate/strong La Niña events, dryness is frequently found across Nebraska, western Kansas, Colorado and Texas during the critical heading period in April and May, when moisture needs are greatest. "The combination of poor establishment and stress during heading results in reduced yields which have been seen in previous moderate and strong La Niña years." says Tapley. 

"Looking back at the 10 moderate or strong La Niña events since 1950, winter wheat yields were down on average nearly 3% nationally compared to the trend yield." The biggest departures were found across Kansas, Colorado, Oklahoma and Texas, where yields were 8-15% below trend on average.”