Wetter Fall but Drier Winter with El Nino?


OMAHA (DTN) — Wide swings in precipitation during the upcoming fall and winter due to El Nino have weather agency forecasters cautious about the impact on harvest conditions, river flow and fire potential in the upper Missouri River basin. The region extends from Montana to Minnesota and from North Dakota to Nebraska.

El Nino is the term used to describe the warming of the eastern tropical Pacific Ocean that takes place every few years. This warming alters the weather pattern of the tropics, and can extend its influence over many other areas of the world, including the U.S. Recent temperature readings place the eastern Pacific temperatures at 3 degrees Celsius above average, which is well above the average reading. This warming extends to a depth of approximately 300 meters. Thus, a huge pool of water has the anomalous warmth. This warmer-ocean regime is expected to remain in place for the balance of the year.

“Forecasts have El Nino in effect through the winter into spring,” said Dennis Todey, South Dakota state climatologist. “The likelihood is 90{62211894bbe3543ea27fa51e74e3ab79f2baeee0f4cbac9ff4b15b5bf1d81fd0} or above for this — certainly through this winter.”

The extent of warming in the current El Nino may rival some of the strongest such events in recorded history. “El Nino was strong in 1982-83, and in 1997-98. The readings for those events certainly compare to this one,” Todey said.

The impact of El Nino-adjusted weather patterns on the U.S. is not guaranteed. “Every El Nino is different,” observed Doug Kluck, regional director of the Missouri River basin climate office in Kansas City. Still, there are some large trends which command respect.

One of those features is the prospect for a wet harvest. “September to November precipitation tends to be above normal; it's wetter in the fall,” said Todey. “That can certainly mean harvest delays if it turns very wet.” Todey also cited possible issues with winter wheat planting due to wet fields. In recent history, El Nino conditions were in place during the fall 2009 season, when harvest season was very slow to proceed; in some fields, harvest did not get finished until the following spring.

Looking to winter, the situation changes from too wet to potentially too dry. “Northern states have much less snow during El Nino winters,” Todey noted. This drier trend combines with a forecast for above-normal temperatures to produce a higher range fire risk. “The fire situation is complicated. A more-open winter with less snow cover, along with the warmer temperatures, leads to a higher potential,” Todey said. Fire threats in the region are highest in Montana and Wyoming, where the winter season is forecast to bring above-normal temperatures to these states.

In addition to the warm Pacific tropical waters, a large area of the Pacific Ocean off the west coast of North America — nicknamed “The Blob” — is also commanding forecasters' attention for its potential to affect fall and winter weather. “The question really is what impact that Pacific blob will have,” said Mark Svoboda of the National Drought Mitigation Center in Lincoln, Nebraska. “There is no analog to the state of the oceans right now. There is a lot of warm pool inertia.”


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graphic image provided by NOAA

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