El Nino weakens. And a weakening El Nino could mean a colder, wetter spring that gives way to a hotter and drier summer.

“That's a long-range prediction,” said Tony Lupo, atmospheric scientist in the University of Missouri-Columbia College of Agriculture, Food and Natural Resources. “And long-range forecasts are always difficult.”

He said conditions in the Southwest likely will follow the cool, wet spring pattern and a summer on the warm side of normal. “But precipitation is less certain,” he said. Long-range forecasts indicate “an equal chance for either more or less rainfall but leaning toward drier.”

Lupo said El Nino, a weather phenomenon originating in the central Pacific Ocean that affects weather patterns across the United States, has been weakening for several weeks. “It weakened significantly in early March,” he said, “and we see signs of continued weakening.”

Lupo said the weak El Nino likely will not digress into a La Nina event but revert to a neutral condition until it begins to strengthen next fall. “El Nino usually sets in around December and weakens over the spring and summer.”

He said the possibility of El Nino gaining strength over the next few weeks is remote. “We've seen it happen, the last time in the early 1990s, but usually it weakens to a neutral status or into La Nina.”

La Nina, he said, typically creates worse conditions for agriculture. “It gets hot and dry. The last time we had a prolonged La Nina was in 1954 through 1956. Weather was very hot and dry. Often we get up to three weeks with no precipitation and then a rain that doesn't help much followed by another prolonged drought period.”

Effects of the weakening El Nino likely will influence weather in the Midwest, Lupo said. “It should follow pretty much the same pattern it displays in the Southwest, except for the Northern Plains states, which may be cooler than normal.”

Lupo said El Nino patterns occur for two to seven years and may change into neutral conditions or La Nina.

He said last summer's weather was unusually good for agriculture throughout most of the United States.

e-mail: rsmith@primediabusiness.com