Ag Weather Forum
Bryce Anderson DTN Ag Meteorologist and DTN Analyst

Monday 06/09/14

El Nino Influence Has Likely Begun

OMAHA (DTN) -- El Nino is here. The large-scale warming of the Pacific Ocean and its associated influence on global weather patterns is, while not in full flower, showing up as we move into early summer.

Eastern Pacific Ocean temperatures are above normal, notably near South America. Ocean warming in this area is a key identifier for El Nino. (Courtesy graphic)

A switch in weather patterns across the entire central U.S. -- highlighted by near-general rainfall in the past two weeks with more forecast during the coming seven days, including not just the Midwest, but the drought-affected Southern Plains -- is one tangible item that speaks to El Nino's presence. Another is the formation of Hurricane Amanda in the eastern Pacific off the Mexican coast during the last week of May. With maximum sustained winds of 155 miles per hour on May 25, Amanda became the most powerful May Pacific storm on record.

In the view of DTN Senior Ag Meteorologist Mike Palmerino, both of these large-scale occurrences utilized very warm tropical Pacific waters -- which speak to the presence of El Nino.

"I've been looking at my data set now for over 30 years following the sea surface temperature departures in the central and eastern Pacific -- and they really shot up during the month of May," Palmerino said. "The first half of May found a degree-and-a-half Celsius above normal, and we ended the month of May at 1.3 degrees Celsius above normal for the month overall. Clearly we're seeing an awful lot of warm water in the tropical Pacific right now. And, I think from that perspective, clearly this is an El Nino."

Official weather agencies -- such as the U.S. Climate Prediction Center (CPC) and the Australia Bureau of Meteorology (BOM) -- are not putting the stamp on El Nino just yet. The CPC's early-June analysis notes the chances of El Nino developing as increasing and "... exceeding 65% by summer." In Australia, the BOM highlights "... at least a 70% chance of an El Nino developing in 2014."

Agency criteria specify that El Nino characteristics need to be catalogued for a period lasting several months in order for the event to be official. Yet, not all the categories are in place for El Nino.

"Some of the other parameters like the atmospheric parameters such as the Southern Oscillation Index that would further drive this are really not falling into place yet," Palmerino said. "But I think from the overall perspective of warmer-than-normal sea surface temperatures in the Pacific, we have that ... sea surface temperatures are right at the top of the list and would be under any circumstances -- suggesting that El Nino is underway."

El Nino is important on both sides of the Pacific for far different reasons. In the U.S., El Nino is viewed as a "non-threat" to summer crop production. Its presence in fall and winter suggests that hurricane numbers will be fewer, and precipitation -- and thus, drought relief -- in California along with the Southern Plains will be above normal. In South America, southern Brazil and Argentina also have tendencies for above-normal precipitation, and crop moisture benefits, when El Nino is in session.

On the other side of the ocean, El Nino has a strong relationship with drought in eastern Australia's wheat country as well as the crop areas of Southeast Asia. The India monsoon is also more erratic during El Nino events. In sum, there is a great deal of crop weather impact that is noted with El Nino.

For the rest of this season, Palmerino looks at the question of "Where do we go from here?" as being key to the intensity of El Nino manifestation. "Do we take this (warm ocean temperature pattern) to another level if the other atmospheric parameters kick in -- or if they don't, do the sea surface temperatures recede a bit toward normal in the coming months? That's really the question we're going to be dealing with here," he said.

And, in that regard, the jury is still out. U.S. and Australia forecast models for early June have a wide disparity in the Pacific temperature forecast. The U.S. model features continued warming of the ocean to a consistent 1.5 degree Celsius above normal range, while the Australia model flattens out the temperature differential at around 0.5 degree Celsius above normal. That difference spells out whether El Nino is moderate (U.S. forecast) or weak (Australia forecast).

"The bigger recent change in model forecasts was the Australian model, suggesting that we may be peaking here and may gradually be drifting back towards normal," Palmerino said.

At this point, the Australia BOM forecast is an outlier -- flying solo -- but Palmerino believes there is still enough relative weight to pay close attention to the BOM depiction. "With the respect that everyone has for the Australians and their abilities with the El Nino-SOI, we're going to have to pay a little attention to this forecast now," he said.

Bryce Anderson can be reached at bryce.anderson@dtn.com

(ES/)

Posted at 10:27AM CDT 06/09/14 by Bryce Anderson
Comments (1)
There is no doubt there has been a tremendous amount of moisture hit the High Plains in the past few weeks that is years overdue, but there are still areas that are lacking. Our extreme SW Kansas county has missed most of the big rains as they have generally stayed south or north/northeast of here. Last night we finally recieved around 1/2"+ county wide, but most areas around us have had numerous days with 1"+ rains. I guess the thing we can hope for is that the pattern is there for additional rainfall and one of these days it'll be our turn. Pretty bad when you are jealous of areas that are in Flood Watchs/Warnings.
Posted by Brad Niehues at 1:45PM CDT 06/09/14
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