Ag Weather Forum

Weak La Nina to Influence Winter

Bryce Anderson
By  Bryce Anderson , DTN Senior Ag Meteorologist
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Central Pacific Ocean temperatures are consistently at cool-value thresholds to support identifying a La Nina. (NOAA graphic by Nick Scalise)

OMAHA (DTN) -- It has taken a while, but the U.S. National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) has noted enough cooling in the central equatorial region of the Pacific Ocean to support a judgment of La Nina being in effect. The agency issued a La Nina Advisory Thursday, November 10.

CPC climatologist Mike Halpert noted that central Pacific equator region sea surface temperatures (a region called Nino 3.4) have cooled to more than 0.5 degree Celsius below average; the October value was -0.7 degree Celsius. Forecasts call for this value to remain in effect for several overlapping three-month periods, through about February 2017. And, finally, there are signs that the atmospheric circulation above the tropical Pacific is stronger than average.

"We are placing a 75% chance of La Nina being in effect through the rest of the October-November-December time frame," Halpert said. "This is followed by a 55% chance for La Nina in December-January-February, with the odds then favoring ENSO-neutral during spring 2017."

The announcement of a La Nina Advisory does not change NOAA's forecast for the 2016-17 winter season. "La Nina is already factored into the forecast," Halpert said. Key features include warmer and drier conditions with drought development in large swaths of the southern U.S., and below-normal temperatures with above-normal precipitation in the northern U.S. "Look for the Northern Plains to be cold this winter," Halpert said.

Besides the implication for drought and stress on crops and pastures in the Southern Plains and southeastern U.S., and higher heating costs in the northern states, the CPC La Nina Advisory also noted that "Convection was suppressed over the central tropical Pacific and enhanced over Indonesia." The Indonesia reference is suggestive of more rain for palm oil production areas of southeastern Asia.

There was no indication given about prospects for spring and summer 2017 in the La Nina update. Long-range projections by NOAA call for above-normal temperatures and equal chances of above-normal, normal, or below-normal precipitation during the June-July-August time frame in 2017.

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