"We haven't had a major, widespread drought in the U.S. Corn Belt in the past 22 years," points out Elwynn Taylor, Iowa State University Extension climatologist. "If the current La Nina event that is occurring in the Pacific Ocean this winter continues into summer that will affect the growing season we have in 2011."
The La Nina weather system that brought dry weather to Iowa during last fall's harvest is expected to persist into this spring, increasing the chances of drier- and warmer-than-normal weather in the U.S. Corn Belt in 2011. The U.S. Climate Prediction Center issued that forecast in mid-January.
Just how big of a risk factor La Nina is for 2011 crops depends on the duration and severity of the event. The current La Nina is one of the strongest in the past 60 years and also has similarities to 1973-74, says Taylor. The Midwest had a poor growing season due to dryness in the summer of 1974.
Australia has had bad flooding, drought has hit Argentina's crop
"The similarity of what happened in 1973-74 to what's happening now is enough to get attention," notes Taylor. La Nina's impacts are already being felt by farmers in key growing areas around the globe. Last month Australia experienced its worst flooding in the past 50 years and drought concerns have recently trimmed 2011 crop prospects in Argentina and Brazil.
There remains considerable uncertainty as to whether La Nina will last into summer. If the cycle continues through the spring months, farmers in the U.S. Corn Belt can expect to have a favorable planting season with warm, dry weather, says Taylor. "However, if the La Nina goes on longer, then things won't be so ideal," he adds. "If the La Nina weather event continues into summer, the heat of summer gets here early and we tend to be on the dry side of usual, particularly in the western Corn Belt."
La Nina may spell problems for farmers in the U.S. Corn Belt
A La Nina occurs when surface water temperatures in the central and eastern Pacific Ocean near the equator become cooler than normal. The cooler water in this region shifts the strength and position of the major air flow pattern. This includes the pattern responsible for movement of weather systems from the Pacific eastward through the continental United States and storm activity in the Gulf of Mexico.
The current La Nina event got started in August and September 2010. If it lasts into April or May 2011, "that would be okay with us in the Midwest to have La Nina over with by then," says Taylor. "It would give us a good, dry and warm planting season. Then we could go into hopefully a normal summer. It would be hard to beat that scenario."
Some experts say weather in the U.S. Corn Belt tends to follow what happens in Argentina. They are right, says Taylor. El Nino and La Nina events usually tend to get going fairly strong about Christmas time, which is the middle of the growing season in South America, and that weather pattern usually is still hanging on when the U.S. Corn Belt's growing season begins.
Effects on South America—keep an eye on that area for clues
Argentina was dry in December and January two years ago, too. The La Nina weather pattern took a bite out of Argentina's crop back then, but that La Nina didn't hang around long enough to bother farmers in the U.S. Corn Belt. "That La Nina faded away in the spring and the dry weather took a nip out of the Argentine crop with heat and dryness in 2008, but that drought wasn't near the strength of the one in Argentina in recent months," says Taylor.
How much impact will the current La Nina have on Brazil? If the La Nina stays strong, drought could spread to Brazil. Southern Brazil has already experienced some spotty dryness into 2011. Continued dryness would have an effect on Brazil's soybean crop, while corn is the main concern and Argentina.
Of course, if you are a farmer down there you are concerned about both crops. "The thing about La Nina is, what it does to the southern part of Brazil, it does just the opposite in the northern growing area of Brazil," says Taylor. "It kind of buffers Brazil, as a whole."
For Elwynn Taylor's latest weather updates and analysis on the Web, just Google "Where's Elwynn?" On Twitter, go to twitter.com\ElwynnTaylor.