Released: February 01, 2006

La Niña No Concern – Yet – for Central U.S.

MANHATTAN, Kan. – Central U.S. residents have no reason to worry yet, even though the National Oceanic and Atmospheric Administration (NOAA) confirmed in January that a La Niña weather pattern is affecting U.S. weather.

“Yes, La Niñas can bring droughts and floods, depending on whether you live in the southern or northern United States. And, since Kansas is in the middle, we can experience both,” said Mary Knapp, State of Kansas climatologist, based with Kansas State University Research and Extension.

La Niñas also can shift the year’s odds for tornadoes toward Kansas, she said. Research at Colorado State University suggests the pattern increases the odds for Caribbean and Atlantic hurricane activity, too.

“What you’ve got to keep in mind, though, is that La Niñas affected the nation 17 times in the 20th century. But, only eight were strong enough to have an impact on Kansas weather,” Knapp said.

Plus, NOAA announced the current La Niña is weak and late in forming. As a result, NOAA’s scientists declined to predict whether the conditions will affect U.S. spring and summer weather.

“So far, the correlations to a La Niña winter in Kansas aren’t particularly strong. A lot of other factors, such as blocking high-pressure systems, are also playing a role,” Knapp said. “We should worry if the La Niña remains or increases by March. If so, then the concern will be La Niñas’ tendency to create hot, dry Kansas summers – hotter and drier than normal.”

In general, La Niña weather simply enhances what’s “average,” she explained. In contrast, the more frequent El Niño pattern causes changes from the norm.

La Niñas and El Niños both emerge from an ocean-atmosphere system in the tropical Pacific. For some reason, a “pool” of ocean water there periodically cools (La Niña) and warms (El Niño). Trade winds spread the temperature change to the east, where it affects the position and intensity of the air’s jet streams. In turn, this impact on the atmosphere affects the movement and intensity of storms.

El Niños are the bigger concern now in climate circles.

“Most of the time, our weather is neutral, but the number of El Niños has been abnormally high since 1990,” Knapp said. “So, what scientists are trying to figure out is global warming’s connection – if any – to the El Niño system in the Pacific. The debate sounds a little like ‘Which came first – the chicken or the egg?’”

Kansas experienced a strong La Niña in 1988-89, but the last strong La Niña to affect the state’s weather appeared in 1998 and extended into the 2000, she said. It created a memorable drought, the effects of which were still being felt two years ago.

El Niños, on the other hand, affected U.S. weather in 1986-87, 1991-92, 1993, 1994, 1997. 2002-03, and 2004-05.

“Few Kansans will forget the strongest El Niño on record, which contributed to widespread, severe flooding in 1993,” Knapp said.

If a La Niña or El Niño pattern is strong enough, its effects can be worldwide.

“In the United States, a La Niña usually means wetter than normal conditions in the north and drier than normal conditions in the south. An El Niño mostly brings the reverse,” Knapp said. “In either case, however, the further you get from the West Coast, the less direct and less consistent the impacts are likely to be.”

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward
kward@oznet.ksu.edu
K-State Research& Extension News