MIDWEST CLIMATE: EL NIÑO

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Winter Impacts - Summer Impacts - Midwest Compared to US - Will 2015-16 Have Same Impacts as Previous?

EL NIÑO IMPACTS

As discussed on our Diversity of El Niño page, the strength of individual El Niño event and various climate factors make each event unique.  Thus, the impacts from each El Niño event can differ and predicting these effects can be difficult.   Climatologies of El Niño events have been developed over the past several decades and have found that in general, warmer and slightly drier wintertime conditions occur in the Midwest during El Niño.  More information on conditions during El Niño winters in the Midwest can be found on our Historical El Niños page.

Composite temperature during six strong El Niño winters Composite precipitation during six strong El Niño winters
Composite images of temperature (left) and daily precipitation (right) during six strong El Niño winters.  Image Credit: NOAA Earth System
Research Laboratory. http://www.esrl.noaa.gov/psd/cgi-bin/data/composites/printpage.pl

During the heart of the summer (June, July, and August), El Niño events have a lesser impact on Midwest temperature and precipitation patterns.  El Niño events are usually weaker during the summer months. In addition, El Niño mainly influences the location of the jet stream over North America.  The jet stream is weaker and farther north during the summer months, minimizing the effects of El Niño on weather in the United States.  However, El Nino events can have some impact on summer weather. Because most El Niño events peak in the winter months, there are two different summers to consider during an El Niño event: the summer during El Niño development, and the late spring and summer after an El Niño. 

During the summer of developing El Niño events, temperatures across the Midwest were slightly cooler than normal.  This trend was strongest when Oceanic Niño Index values were already nearing a moderate El Niño during the summer months.  Including 2015, five of the seven strong El Niño events since 1950 had below normal temperatures with four of the seven 1.0°F below normal or more.  Precipitation deviation from normal was less during those same years, with summer precipitation staying within five percent of normal in five of the seven summers.  2015 and 1991 were outliers, with precipitation percentages around 25% above and below normal, respectively. 

Temperature ranks and departures during the summer before a strong El Niño winter   Precipitation ranks and departures during the summer before a strong El Niño winter
Midwest Temperature (left, °F) and Precipitation (right, inches) ranks and departures from the 1981-2000 normals during the summer prior to
a strong El Niño winter. Ranks are from warmest to coldest and wettest to driest, respectively.  Ranks with a "T" represent a tie. Data are
based on the nClimDiv dataset from NCEI with a period of record from 1895-2015.

During the summer after an El Niño event, there was no tendency for above or below normal temperatures or precipitation in the Midwest. Impacts were more likely to occur during the transition from spring into summer (May-June-July). A climatology of temperature and precipitation during that three month period was developed for El Nino events from 1950-2010 and found that temperatures were 0.5°F to 1°F cooler on average across Minnesota, Wisconsin, and Michigan.  Precipitation was enhanced across the central Midwest during that same timeframe.

Temperature ranks and departures during the summer after a strong El Niño winter   Precipitation ranks and departures during the summer after a strong El Niño winter
Midwest Temperature (left, °F) and Precipitation (right, inches) ranks and departures from the 1981-2000 normals during the summer after a
strong El Niño winter. Ranks are from warmest to coldest and wettest to driest, respectively.  Ranks with a "T" represent a tie.  Data are
based on the nClimDiv dataset from NCEI with a period of record from 1985-2015.

The Midwest’s economy depends on both summer and winter conditions for cash crops, specialty crops, recreation, transportation, and energy. Knowing how weather conditions can be impacted during an El Niño event is important for these industries and consumers.  Below, impacts from the 1997-98 El Niño winter and general summertime impacts are presented.

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Wintertime Impacts of the 1997-1998 El Niño in the Midwest

Read the full report for the Midwest

While El Niño events have been occurring for centuries, it wasn’t until the 1997-98 El Niño event that the public understood the potential wide-spread impacts El Niño events can have.  Because of this, very few studies on the impacts of El Niño have been completed for events other than the 1997-98 El Niño winter.  These were the impacts from that winter on the Midwest, which was exceptionally warm with less snowfall and precipitation than normal.

Benefits to Industry and Society during the Winter Season due to El Niño Conditions in the Midwest

Negative Impacts to Industry and Society during the Winter Season due to El Niño Conditions in the Midwest

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Possible Summertime Impacts Due to El Niño in the Midwest

The four Ninñ regions
July precipitation, deviation from 1950-2013 average, during El Niño years using PRISM monthly data.  El Niño classifications are based on the Multivariate ENSO Index (MEI). Map Credit: http://agroclimate.org/

During the summer months, determining the impacts of El Niño is more difficult as El Niño plays a less prominent role in overall weather patterns in the region. 

The few impacts that may have been present were primarily felt by the agriculture sector.  Enhanced precipitation levels during the May through July period may have impacted plants during critical times in their growing season development.  Cool and wet Julys have been generally considered good for corn yields, and El Niño summers have had above normal precipitation in the western portions of the region during that month.  However, early rains in May and June may disrupt crop development and lead to degraded crop conditions as was the case across Missouri through Ohio in May-June 2015.  Whether these impacts are caused by the El Niño event could be debated.

Possible El Niño Impacts to Corn and Soybean Yields

El Niño impacts to agricultural production have been investigated extensively across the United States.  The tables below show corn and soybean yields in Midwestern states before and after the defined strong El Niño years on our Historical El Niños page.  In the summers when a strong El Niño was developing, detrended corn and soybean yields were generally above the 2010-2014 5-year average.  

Detrended Midwest state yield data - 1957

Detrended Midwest state yield data 1958
Detrended Midwest state yield data from the 1950-2014 yield average.  Yield data detrended to account for technological improvements in crop
production.  Greens indicate an increase in yield compared to the 2010-2014 5-year average yield, while browns, oranges, and golds indicate a
reduction from the 5-year average.  Data source: National Agricultural Statistics Service

In the summers after a strong El Niño, there was not a strong impact on crop yields.  The detrended average of these years compared to the 2010-2014 5-year average shows most yield differences for the summers after an El Niño are 5 percent or less, except in Kentucky and Missouri for corn and Indiana for soybeans.  The major drop in yields in 1983 were attributed to a drought across the region. 

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How do El Niño Impacts in the Midwest Compare to the Rest of the United States?

While the Midwest experienced negative impacts from the 1997-98 El Niño event, they were not as great as in other parts of the United States and North America.  Heavy rain and snow fell across California during the winter of 1997-98, bringing 20 or more inches of precipitation to over half the state.  Areas along the northern California coast had upwards of 50 inches for the winter.  Flooding and landslides were prevalent across the state due to the excess precipitation, causing damage to agriculture as well as homes.  In the Northeast U.S. and Canada, intense ice storms occurred in January as warmer than normal temperatures stabilized around the freezing point during the storms.  Tornadoes tore a path through Florida in February 1998 while other southern states experienced an abnormally high number of wintertime severe weather events.  Hawaii also was impacted as an El Nino-related drought formed from changed weather patterns in the Pacific Ocean, depleting water reservoirs. 

These impacts on other areas of the United States and Canada totaled in the billions of dollars.  While ski lodges and snow lovers may disagree, the positive economic impacts of El Niño in the Midwest from lower heating costs and increased shopping activity outweighed the negative impacts from warmer temperatures and less snow and precipitation in 1997-98. 
 

Will the 2015-16 El Niño Have Exactly the Same Impacts as the 1997-98 El Niño?

As explained in our Diversity of El Niño page, not all El Niño events are created equal.  El Niño events can produce different temperature and precipitation patterns across the United States, resulting in differing impacts. Of the many El Niño events that have occurred, the 1997-98 El Niño event was one of the only El Niño events that has been studied for its impact on society and industry.  After the 2015-2016 El Niño, it will be imperative to once again look at how El Niño impacts the weather in the Midwest and throughout the United States. 

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External Source: Changnon, Stanley A.  El Niño 1997-1998: The Climate Event of the Century.  Oxford University Press, 2000. Print.