Cool, wet U.S. Midwest | A warming central Pacific and a cooling in the eastern Pacific could worsen drought in western U.S.
It is becoming apparent that an El Nino is forming, but for now it looks to be an unusual version, says a weather forecaster.
There has been a distinct warming in Pacific Ocean temperatures in the past couple weeks, but the warming is occurring in the central tropical Pacific.
A typical El Nino is associated with a warming trend in the eastern equatorial Pacific where ocean temperatures have been cooling.
A warming in the central Pacific combined with a cooling in the eastern Pacific is indicative of the development of an El Nino Modoki phenomenon, which delivers different weather patterns to North America than a typical El Nino.
Scott Yuknis, lead forecaster with the Climate Impact Co., said it would likely result in a dry and hot growing season in Western Canada, wet and cool conditions in the U.S. corn belt and dry and hot weather further south in the winter wheat growing area of the Great Plains.
The ridge pattern over Alaska, which has caused the cool weather in Western Canada this winter, would shift south and east, setting up over the western portion of North America.
“Western Canada would be dry and the summer would likely be hot,” said Yuknis.
The western half of the United States would experience similar conditions, exacerbating the growing drought in that region of the U.S.
Conditions in the Great Plains and Midwest regions of the U.S. would be a flip-flop of what would typically happen under El Nino conditions.
It would be unusually wet in the corn belt, which would suppress the summer heat.
States in the western Plains would experience a mixture of the hot and dry weather in the western U.S. and the cool and wet conditions in the Midwest.
“The western Plains are going to be in and out of the hot weather but not persistent in it,” said Yuknis.
An El Nino Modoki would tend to deflect tropical cyclone activity forming in the Gulf of Mexico, preventing important late-summer rainfall from moving north across Texas and into the southern Plains.
“That really is the best way to generate important rainfall once we get into the second half of summer,” said Yuknis.
“That tells me we would be reliant on spring rains to prevent central U.S. drought.”
He believes the spring rains will happen in the Midwest but not in the western and southwestern Plains.
There has been plenty of wet snowfall in the Midwest during the second half of winter. That means good soil moisture, which reinforces the prediction for wet and cool conditions in the spring and summer in that important region for corn and soybean production.
However, there is a risk of drought amplifying in the winter wheat growing areas of Kansas, Oklahoma and Texas under an El Nino Modoki scenario.
Yuknis said the big lingering question is whether the warming in the central Pacific is persistent enough that it eventually breaks down the cooling pattern in the eastern Pacific and causes a traditional El Nino to form, which would change the forecast once again.