Ag Weather Forum

Let's Keep Perspective On El Nino

Bryce Anderson
By  Bryce Anderson , Ag Meteorologist Emeritus
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Pacific Ocean sea surface temperatures are indeed above normal in the central ocean, but show a slight cooling trend in the eastern half. (NOAA graphic)

The National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC) caused quite a storm of discussion (pun intended) Thursday March 5 with the issuance of an El Nino Advisory. The advisory was issued because a combination of central Pacific Ocean water temperatures, subsurface temperature trends, and the Southern Oscillation Index value over the past couple months led to the assessment that "...these features are consistent with borderline, weak El Nino conditions." (bolded print is mine)

This announcement led to a "What is up with that?" type of question in our DTN ag weather group. We -- and several state climatologists who I discussed things with -- are wondering about what led NOAA to this conclusion at this time. This particular pronouncement, frankly, does not make much sense. Here's why:

In the first place, the Pacific Ocean sea surface temperatures do not show a "classic" El Nino trend. There is indeed warm water in the central and west-central Pacific areas, but the eastern Pacific -- from South America to the International Date Line -- is actually showing some cooling. Eastern Pacific temperatures logged by my colleague Mike Palmerino show that December, 2014 had the sea surface temperatures in the eastern Pacific at 1.4 degrees Celsius (just under three degrees Fahrenheit) above normal (warmer temperatures are part of El Nino), with that trend declining in both January and February to just a plus zero-point-four (0.4) degree Celsius (.8 degree Fahrenheit). That cooling is certainly not in keeping with El Nino descriptions.

Another measurement of the El Nino feature -- the barometer relationship between the island of Tahiti and Darwin, Australia (far northern Australia) that is expressed in the Southern Oscillation Index (SOI) and tracked by the Australia Bureau of Meteorology (BOM) -- is also showing a non-El Nino type reading. As of Friday, March 6, the SOI daily reading was -2.8; the 30-day running average was +0.8; and the 90-day average was -5.2. For the previous three months, the SOI actually moved from borderline El Nino values of -7.6 for December and -8.7 in January, to a -0.5 in February. That is "neutral" territory.

To complete a three-point rejoinder to the pronouncement -- the CPC is flying solo a bit in this assessment. The Australians have noted an El Nino "watch" -- but that is still two levels away from saying that El Nino is in effect. And the latest Japanese weather bureau Pacific assessment -- dated February 10 -- stated that "El Nino conditions are decaying in the equatorial Pacific." Its forecast for the Pacific last month noted a 50-50 chance for redevelopment of El Nino during the spring 2015 season. The Japan agency's forecast will be updated this coming Tuesday, March 10.

So, where does that leave us regarding the Pacific's weather influence on crop weather for this spring? While we have seen some El Nino flavor to the pattern in the last week or so with the heavy precipitation from the southwestern U.S. through the Northeast -- including record snows in the Delta and the Ohio Valley -- along with the outrageous extreme cold in the southern and eastern U.S. along with the eastern Canadian Prairies through eastern Canada. The drier and warmer conditions over the Northwest, the northern Plains, northern Midwest and the western Canadian Prairies are also characteristics of an El Nino. But, whether those features continue is questionable. After all, a weak El Nino is different than a moderate to strong event.

As to a forecast -- the analogs for this season, with a weak El Nino, still look warm in almost all crop areas. The Midwest is drier, which would be favorable for field work. In the Delta and Southeast, the pattern is wetter. Southern Plains areas have additional chances at moisture, and the Far West drought continues. Northern Plains locales have generally above normal temperatures with a big disparity in precipitation -- near normal east of the Missouri River, but below normal west.

It will also be interesting to see further updates from the Climate Prediction Center regarding this latest El Nino pronouncement.


Twitter @BAndersonDTN


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