Post-La Nina Weather Unclear

Two-Year La Nina Event Over, But Picture of this Year's Crop Weather Uncertain

The 2011-12 La Nina in the Pacific Basin has ended, according to a March 27 bulletin issued by the Australia Bureau of Meteorology.

There are still plenty of questions regarding the weather patterns over the major North American crop areas even with the official ruling that La Nina is over. (DTN file photo by Eleanor Anderson)

The Australia bureau bases its evaluation of La Nina ending largely on a months-long trend in the Southern Oscillation Index (SOI). This index has remained within neutral values since mid-to-late February and in the 30 days ended March 25 measured at plus-7.1. The parameters for a La Nina event call for sustained SOI values of 8 or above. The SOI is an index based on comparing the barometric readings on the island of Tahiti in the tropical Pacific with those from Darwin on the northern coast of Australia. It can be argued that this La Nina actually began in June 2010 and, following a brief decline in intensity in the spring a year ago, resumed during the summer and fall seasons.

In addition to the trend in the SOI number, Pacific Ocean temperatures, both at the surface and in sub-surface waters, have warmed notably since the first of the year. La Nina features below-normal Pacific temperatures.

During its lifetime, this was a moderate to strong La Nina. It is cited as a contributor to such catastrophes in 2011 as violent tornado outbreaks, flooding in the Ohio-Mississippi river basins and in the Missouri River basin, the historic drought that caused billions of dollars in damage to Southern Plains agriculture, and the Midwest flash drought that reduced corn production relative to projections for the second straight year.

But, whether La Nina's end is a sign of favorable conditions for the entire 2012 growing season is uncertain, according to Telvent DTN Senior Ag Meteorologist Mike Palmerino.

"There still are several different ways this could play out," Palmerino said. "Do we stay neutral for the rest of this year? Do we start having more weather features that hint of an El Nino developing? Do we somehow have a resurgence of La Nina patterns? It's still undecided."

What's happening right now, Palmerino said, is a volatile weather pattern across North America that seems to have its own identity.

"It's just amazing -- there's no relation to what we've seen in the U.S. recently and the demise of La Nina," he said. "In fact, the way this pattern is going, the next real concern is how cold it gets during mid- to late next week with all the implications of that for emerged corn and heading wheat."

Bryce Anderson can be contacted at bryce.anderson@telventdtn.com

http://www.dtnprogressivefarmer.com/dtnag/common/link.do?symbolicName=/free/news/template1&paneContentId=5&paneParentId=70104&product=/ag/news/topstories&vendorReference=03c04f6a-bd64-4713-ac52-9066f87bb730