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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.

This information is not for you to base your market plan for 2020 on a drought, but it does mean, more than normal, you need to have a plan if prices go sharply higher after you price corn and beans.

By the way, here is the water temperature chart from Mar 2019. Note the water temperature was more than a half degree C above normal for more than 60 days, which is my definition of an EL NIÑO episode. As a grain market person, you should be able to take a glance at a chart like this and say to yourself, “It is going to be a wet spring!” and adjust your spring operational plan accordingly:

As you may recall, 2019 was a “little” wetter than normal. You can also see wet fall of 2018 was quite predicable from mid to late summer that year.

Impact of ENSO stages around the world are:

El NIÑO impact

Wet & cool:

  • Corn Belt

  • Southern Brazil and Argentina

  • Black Sea Area (Eastern Europe)

Drier and warmer:

  • Central and Northern Brazil

  • Western Europe

  • Southern Africa

  • Australia

La NIÑA impact

Wet and cool:

  • Central and Northern Brazil

  • Australia

  • Western Europe

  • Southern Africa

  • China, wet & cool in the southeast area with many typhoons; hot & dry in the northeast area.

  • Malaysia, the Philippines, and Indonesia (palm oil areas) wet and cool.

Warmer and drier than normal:

  • Corn Belt

  • Southern Brazil and Argentina

  • Black Sea Area (Eastern Europe)

  • Northern Africa

The following pages are the month-by-month ENSO reports with NOAA’s official statement followed by Roger’s comments.

The purpose of this presentation is to present the evidence to you why following ENSO updates is valuable.


August 2018

NOAA issued its ENSO update yesterday. Their official statement: ENSO Alert System Status: El Niño Watch

Synopsis: There is ~60% chance of El Niño in the Northern Hemisphere fall 2018 (September-November), increasing to ~70% during winter 2018-19.

Roger’s comment:

The chart of surface temperatures of the Equatorial Pacific Ocean shows a more than half degree C above normal temperature continued during the month of July. That means we (Corn Belt people) will continue to see above normal rainfall until that water temperature begins a sharp decline or slowly returns to normal.

September 2018

The EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION was issued this morning issued by the CLIMATE PREDICTION CENTER/NCEP/NWS and the International Research Institute for Climate and Society. Their official statement:

ENSO Alert System Status: El Niño Watch

Synopsis: There is a 50-55% chance of El Niño onset during the Northern Hemisphere fall 2018 (September-November), increasing to 65-70% during winter 2018-19.

Roger’s comment:

There are presently 8 tropical depressions, storms or hurricanes in the Atlantic Ocean. Typically, during an El Nino episode, there are very few tropical storms. I would not have been surprised to see the surface water temperature of the Equatorial Pacific decline in recent weeks, but, as you can see in the chart below, it has not.

One must conclude that above normal rainfall will continue in much of the Corn Belt, especially the Eastern Corn Belt, into the fall.

October 2018

NOAA's Official Statement ENSO Alert System Status: El Niño Watch

Synopsis: El Niño is favored to form in the next couple of months and continue through the Northern Hemisphere winter 2018-19 (70-75% chance).

The graph of Equatorial Pacific Surface Water Temperatures Deviation from Normal:

Roger’s comment:

The graph shows the water temperature increased almost a half degree C during the month of September and is now 1.35 degrees C above normal. That will cause a very serious series of unusual weather events around the world. We already have drought in Australia, dry weather in Eastern Europe and wet weather in Western Europe and the Corn Belt. Now you can see why rainfall increased the past month in the Upper Midwest. It will probably continue through harvest in the US.

The probability of weather problems boosting corn, wheat and soybean prices in the next few months just increased by five-fold. Why?

In the old days, before we so politically correct, the weather people employed by government would pointedly state that an El Nino Episode was officially in effect when the Pacific Equatorial water temperature was a half degree C above normal for 60 consecutive days. We have had that aberration since early April (look at the chart!). Now the water temperature aberration is twice the magnitude it was all summer. Likewise, the unusual weather around the world will be much more extreme. Did anyone besides me notice the weather in September got more unusual in many places around the world? Fasten your seat belts!

Now that we are politically correct, government officials will not say anything to hurt your precious ego or cause you stress. We have had an El Nino all summer and now it’s going to get a lot more severe. That means drier than normal in Brazil and wetter than normal in Argentina. The dry weather in Eastern Europe and Australia will get worse.

Last winter's La Nina (the opposite of El Nino) made Brazil wet and Argentina dry. It is highly likely Brazil will be dry and Argentina and Paraguay will be wet in the coming months and, that Ladies and Gentlemen, is where nearly almost two-thirds of the world's soybeans are grown (about 63%). Wheat markets will also benefit as world-wide weather anomalies will impact wheat crops everywhere and, in most places, not for good.


Whole article and November 2018 though May 2021 period are in this PDF document:

Cause and Effect of El Niño and La Niña Episodes
Download PDF • 1.78MB


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