sealPurdue News

June 20, 1997

El Niño returns, could upset Indiana weather -- so what's new?

WEST LAFAYETTE, Ind. -- Like people in many states, Hoosiers love to brag about the unpredictability of their weather. This spring has been consistently cool and wet. But, if you wait a few minutes...

It appears that the weather pattern known as El Niño is reemerging in the Pacific Ocean, and that could bring a change for Indiana weather for next winter, and perhaps for the next few years. The near-record setting cold that we've experienced off-and-on for the past few years could be replaced by unseasonable warmth.

Ken Scheeringa, acting state climatologist for Indiana, stationed at Purdue University, says that the last major El Niño fifteen years ago caused memorable changes in our weather.

"It appears that El Niño is roaring back, and this one is showing signs it could become more intense than the one in 1982-83," he says. "That year was when we had the Christmas day in the 60 degree range."

The effects of El Niño are always the most apparent near Christmas, and the name "El Niño" refers to the Christ child.

"What we're in now is the opposite of an El Niño," Scheeringa says. "We're feeling the influences of a weather pattern known as 'La Niña.' With this the ocean surface temperatures are cold, and since the end of last year and the beginning of this year we have been in a predominately cool weather pattern. That's why we've seen such cool temperatures this past winter and into the spring.

"That appears to be changing, perhaps in a very intense way," he says. According to Scheeringa, the El Niño weather pattern could bring unusually warm and dry weather to the Midwest, especially in the winter months.

El Niño weather patterns occur every few years, most recently during the winters of 1994-95 and 1987-88. The last major El Niño occurred during the winter of 1982-83. That winter, storms caused damage in California and the Gulf States resulting in an estimated 100 deaths and more than $2 billion damage.

Early predictions by the National Weather Service say that this El Niño is even more severe than the 1982-83 episode.

Dayton Vincent, professor of atmospheric sciences at Purdue, says there is some disagreement among researchers about what causes El Niño, but there some characteristics that all weather scientists agree on.

Vincent says two events happen nearly simultaneously to create the weather pattern known as El Niño. "Water over the eastern Pacific, especially just south of the equator, becomes much warmer than normal during December and January," he says. "The second occurrence is that low-level winds from the region stretching from the western Pacific to east of the International Dateline become more westerly or, at least, less easterly than normal. This actually causes upwelling in the ocean circulation, and warmer waters come to the surface over the central Pacific to join those already over the eastern Pacific."

According to Vincent, wind changes in the lower atmosphere and in the Pacific Ocean cause a change in upper atmospheric circulation patterns. It's this upper atmospheric weather pattern, near jet stream levels, that ultimately influences weather in the United States, he says.

"It's well established that the southeastern part of the United States will see more cyclonic activity, and the northern Great Plains and south-central Canada will have more high pressure, so there are fewer storms and less rainfall," Vincent says. "In the Midwest, we lie in a zone that makes it difficult to tell if El Niño affects our weather. This spring we've had a lot of storms to the south while northern Minnesota and northern Michigan had better than normal weather. This could well be associated with the beginning El Niño conditions."

Ralph Gann, U.S. Department of Agriculture State Statistician for Indiana, says for farmers in the Eastern corn belt, the El Niño weather pattern could be good news. "The years El Niño was in effect in the 1980s we had record-setting yields, except in 1988 when we had a major drought," he says. "What's unsettling to many farmers is the increasing volatility of the weather. The past decade has been more erratic than the previous two decades, and that makes it hard to plan for the crops."

More information about the coming El Niño can be found on the Internet at these sites:

Sources: Ken Scheeringa, (765) 494-8105; e-mail,
Dayton Vincent, (765) 494-3290 e-mail,
Ralph Gann, (765) 494-8371
Writer: Steve Tally, (765) 494-9809; e-mail,
Purdue News Service: (765) 494-2096; e-mail,

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