Grain and oilseed crops may be threatened next year by a weather pattern known as La Nina, according to a private forecaster.La Nina conditions have developed rapidly across the equatorial Pacific Ocean during the past few weeks, said Drew Lerner, president of World Weather Inc. in Overland Park, Kansas. He said that may indicate more dry weather in parts of South America in the next three months and a wet, cold start to the U.S. planting season in March.
La Nina, which means “the little girl” in Spanish, is caused by lower-than-normal surface-water temperatures in the Pacific. It can trigger widespread changes in weather around the world, including a higher-than-normal number of hurricanes in the Atlantic Ocean, Lerner said.
“The impact of La Nina conditions has already been noted in many areas, with more frequent rain in eastern Australia, wet weather in Indonesia, Malaysia and the Philippines as well as a drier bias in southeastern parts of South America,” Lerner said in a Dec. 24 interview. “Confidence is quite strong that a full blown La Nina event is evolving.”
The current weather patterns are more similar to a mature La Nina instead of a developing event because the last episode faded in May, leaving behind residual atmospheric conditions, Lerner said. The pocket of unusually cool Pacific water has quickly expanded west and extends to a greater depth than usual, signaling a stronger impact on next year’s weather, he said...MORE
Although the PDO and La Nina are different events, the cool phase of the PDO exhibits a tendency toward more La Nina's and fewer El Nino's. We are not currently experiencing a La Nina (defined as three consecutive months of -0.5 degree Sea Surface Temperature anomaly).
A couple weeks ago NASA came out with a statement (here relayed by ScienceDaily):
Oscillation Rules As The Pacific Cools
The latest image of sea-surface height measurements from the U.S./French Jason-1 oceanography satellite shows the Pacific Ocean remains locked in a strong, cool phase of the Pacific Decadal Oscillation, a large, long-lived pattern of climate variability in the Pacific associated with a general cooling of Pacific waters. The image also confirms that El Niño and La Niña remain absent from the tropical Pacific....
A cool wedge of lower-than-normal sea-surface heights continues to dominate the tropical Pacific, ringed by a horseshoe of warmer waters. The continuation of this long-term cool phase of the Pacific Decadal Oscillation stacks the odds against a wetter-than-average winter/spring in the southwestern United States. (Credit: NASA/JPL)"This multi-year Pacific Decadal Oscillation 'cool' trend can cause La Niña-like impacts around the Pacific basin," said Bill Patzert, an oceanographer and climatologist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The present cool phase of the Pacific Decadal Oscillation will have significant implications for shifts in marine ecosystems, and for land temperature and rainfall patterns around the Pacific basin."
According to Nathan Mantua of the Climate Impacts Group at the University of Washington, Seattle, whose research contributed to the early understanding of the Pacific Decadal Oscillation, "Even with the strong La Niña event fading in the tropics last spring, the North Pacific's sea surface temperature anomaly pattern has remained strongly negative since last fall. This cool phase will likely persist this winter and, perhaps, beyond. Historically, this situation has been associated with favorable ocean conditions for the return of U.S. west coast Coho and Chinook salmon, but it translates to low odds for abundant winter/spring precipitation in the southwest (including Southern California)."...MORE
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