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Cause and Effect of El Niño and La Niña Episodes

ENSO Explanation

written May 2020

The US Government’s National Atmospheric and Oceanic Administration (NOAA) issues El Nino/Southern Oscillation (ENSO) report the second Thursday of every month. ENSO is a recurring climate pattern involving changes in the temperature of equatorial waters in the central and eastern Pacific Ocean. This oscillating warming and cooling pattern, referred to as the ENSO cycle, directly affects rainfall distribution around the world. El Niño and La Niña are the extreme phases of the ENSO cycle; between these two phases is a third phase called ENSO-neutral.

ENSO affects Australian weather more so than any other crop area of the world and the Aussie government devotes much of its resources to track and report ENSO information twice a month.

I track ENSO reports. The following is the monthly summary from NOAA from August 2018 and my corresponding analysis of the same set of facts. I have found NOAA monthly reports are the most reliable 30 to 60 day forecast tool for world weather.

Predicting weather with accuracy is the key to predicting grain prices.

For more than 500 years, the world knew when millions of dead anchovies washed-up on the beaches of Ecuador and Peru, the world's weather was about to change, but no one knew why. The search for the "Holy Grail" of weather forecasting was to figure out why those anchovies died.

Fifty or so years ago, we learned the anchovies died due to a rapid change of the temperature of the Pacific water west of Peru. Research efforts then focused on what caused the water temperature to change and, more importantly, how to predict weather as a result of the temperature change.

The science of monitoring and evaluation of the wind direction and the temperature of the wind and surface water of the Equatorial Pacific and Indian Oceans is called EL NIÑO/SOUTHERN OSCILLATION (ENSO).

I have learned ENSO influences on weather is, by far, the most reliable long-term predictor of world weather. Of course nothing is 100% in this business; if it was, we all would be rich.

After decades of following ENSO data, I usually disagree with the professionals' weather predictions based upon ENSO data. I have learned the water temperature of the Pacific Ocean impacts Corn Belt weather far more than water temperature in the Indian Ocean or wind temperature and direction in either ocean.

There are three phases of ENSO, namely Neutral, El NIÑO and La NIÑA.

El NIÑO springs and summers bring cool and cloudy weather with above normal rainfall to the Corn Belt. In an El NIÑO year, the biggest risk to the corn crop is not getting it planted, but if the corn gets planted, the national average yield will most likely be a record large as improved technology and great growing weather allows the plant genetics to do their thing. Soybeans do not do as well as corn El NIÑO growing season as wet soil enhances fungi diseases.

The cool, cloudy weather will hinder maturity, harvest will be late and the corn will be wet. You need to price your price your corn early and your beans late in an El NIÑO growing season. Likewise, buy your propane early in such a year.

La NIÑA brings drought with above normal temperatures to the Corn Belt. The 1983, 1988, 2002 and 2012 Corn Belt droughts were La NIÑA years. La NIÑA episodes curtail Atlantic Ocean hurricanes. Note the 1980 Corn Belt drought was not caused by a La NIÑA episode. That drought was a result of Mt. St. Helen's eruption on 18 May 1980.

The longest El NIÑO was from the early summer of 1992 through the growing season of 1994. The 1992 and 1994 corn crops were record large yields, but 1993 was the flood year. Satellite photos in late June 1993 showed Lake Superior extended all the way to St. Louis. Record corn yields in 2004 and 2009 were a result of ever improving technology and El NIÑO episodes. Hurricanes in the Atlantic are usually more frequent during El NIÑO years, so you folks in the Southeast beware.

There are varying strengths of the ENSO episodes with varying degrees of impact. Australia is ground zero for the extremes of the ENSO episodes. Consequently, the Aussies dedicate a lot of resources to ENSO analysis. They issue an ENSO report twice a month and post it at:

The US National Oceanic and Atmospheric Administration (NOAA) issues their ENSO analysis the morning of the second Thursday of every month. It is usually five to six pages of the most complicated technical crap this side of the US government IRS tax code. The good news is, as a farmer, 90% of everything you need to know about ENSO is in the twelve-month graph of Equatorial Pacific water temperatures. The other 10% you need to know is NOAA's synopsis stated at the top of the first page of NOAA’s report. NOAA’s monthly report is at:

This is what watching ENSO data for decades have taught me:

  • If the water temperature is a half degree C below normal for 60 consecutive days, a La NIÑA episode has already begun.

  • Rapidly falling water temperatures will bring La NIÑA like weather for a few weeks.

  • If the water temperature is a half degree C above normal for 60 consecutive days, an El NIÑO episode has already begun.

  • Rapidly rising water temperatures will bring El NIÑO like weather for a few weeks.

The way I keep the two extremes straight is to associate cool water with low evaporation rates, which will keep the air moving northeast to the Corn Belt drier than normal, hence less rainfall. Whereas, warmer than normal water will evaporate at a higher rate and put more water in the air to move across the Corn Belt. More water in the air means more clouds and rain. The NOAA ENSO update issued May 14, 2020 was summarized by the professional weather people this way:

EL NIÑO/SOUTHERN OSCILLATION (ENSO) Synopsis: There is a ~65% chance of ENSO-neutral during Northern Hemisphere summer 2020, with chances decreasing through the autumn (to 45-50%).

The water temperature chart that date:

My comments for that date were: Dry weather is coming to the Corn Belt after mostly normal weather for the next two to three weeks because the water temperature is falling so rapidly. I know that is not a highly complex explanation, but that is all you need to know.

Note the Australian Bureau of Meteorology has eight computer models to track ENSO changes. In March, two of those eight models predicted a La Nina episode this late spring and early summer. Since then, three of the eight models predict a La Nina, which, once again, brings hot and dry weather to the Corn Belt… think 2012, 2008, 1988 and 1983… The similarities between this spring and the spring of 1988 are quite surprising.