The impact of La Nina will likely slowly decline over the coming months, the United Nations weather body said Friday, but warned that the possibility of the reappearance of the weather phenomenon could not be ruled out.

"La Nina conditions are expected to persist until March-May 2012. Currently, expectations beyond May 2012 are uncertain. While neutral conditions appear likely, possibilities for development of El Nino, or even redevelopment of La Nina, cannot be ruled out," the WMO warned.

Sentiment toward commodities lying in the traditional path of La Nina started to turn more bullish at the end of last year, as Chicago and European futures grain markets advanced on fears over crop conditions in South America.

Climatologists and commodity analysts have blamed La Nina for the recent drought in Argentina that ravaged the country's corn crop.

Argentina's farmers were expected to harvest a record 30 million metric tons of corn in the 2011-12 season, but analysts say about a third of that potential output has evaporated because of hot, dry weather blamed on the La Nina weather phenomenon.

La Nina is a periodic climatic phenomenon that brings more rain to the western Pacific, and to a lesser extent, to the eastern Pacific.

Analysts also blamed La Nina for damaging the U.S. wheat crop and dryness across the U.S. corn belt last year.

The harvest in Texas, the country's second-largest producer of high-quality, hard red winter wheat, dropped nearly 60% last year to a five-year low of 52 million bushels. Winter wheat is planted from late August through October and then harvested the following spring. Some serves as a feed for cattle, which graze on it.

Still, William C. Patzert, climatologist at the National Aeronautics and Space Administration warns that this year's La Nina will certainly hold some surprises and warned drought in the U.S. corn and wheat belt has the strong possibility of repeating itself.

-By Neena Rai, Dow Jones Newswires; 4420-7842-9450; neena.rai@dowjones.com.
(END) Dow Jones Newswires
February 10, 2012 05:33 ET (10:33 GMT)