National Weather Service United States Department of Commerce

 

Climate.gov's El Nino/La Nina page

 

Current Conditions

  • El Niño conditions are ongoing.
  • El Niño advisory in effect.
  • El Niño will gradually weaken this spring.
  • One of the strongest El Niño's since reliable records began in 1950, with similar strength to 1982-83 and 1997-98.

 

Tropical Pacific Sea Surface Temperatures Tropical Pacific Sea Surface Temperature Anomalies
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Tropical Pacific sea surface temperatures (left image) and associated anomalies (right image).  Notice the unusually warm strip of sea surface temperatures oriented west to east across the central and eastern equatorial Pacific Ocean, typical of El Niño conditions.

 

Quick Facts

  • Moderate to strong El Niño/La Niña episodes pose a greater chance of affecting Kentucky weather compared to weak episodes.
  • Meaningful impacts for Kentucky and Indiana are most common from mid winter through spring.

What are El Niño and La Niña?

  • El Niño: Above-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean.  Over Indonesia, rainfall tends to become reduced while rainfall increases over the tropical Pacific Ocean.  The low-level surface winds, which normally blow from east to west along the equator (“easterlies”), instead weaken or, in some cases, start blowing the other direction (“westerlies”).
  • La Niña: Below-average sea surface temperatures (SST), in the central and eastern tropical Pacific Ocean.  Over Indonesia, rainfall tends to increase while rainfall decreases over the central tropical Pacific Ocean.  The normal easterly winds along the equator become even stronger.

 

Maps of sea surface temperature anomaly in the Pacific Ocean during a strong La Niña (top, December 1988) and a strong El Niño (bottom, December 1997). Maps by NOAA Climate.gov, based on data provided by NOAA View.

 

El Niño and La Niña are two of the most important climate phenomena on Earth due to their ability to change the global atmospheric circulation, which in turn influences temperature and precipitation across the globe.  We also focus on El Niño and La Niña because we can often predict their arrival a few seasons in advance of the strongest impacts on weather and climate

How did El Niño get its name?  South American fisherman noticed a warm up of coastal waters that occurred every so often around Christmas.  They referred to the warming as “El Niño,” (niño being Spanish for a boy child) in connection with the Christmas holiday. In the 1980s the term La Niña began being used for the cooling of those waters.

Typical late fall through early spring upper level jet stream positions associated with moderate to strong La Niña (left) and El Niño (right) events.  During La Niña, a variable Pacific jet stream in association with a polar jet stream shifted further south favors below normal precipitation across the southern US, with below normal temperatures across the northern US.  During El Niño, a strong and amplified Pacific jet stream extending across the southern US in association with a polar jet stream shifted further north into Canada favors above normal precipitation across the southern US, and above normal temperatures over the northern US.  Based on original graphics from NOAA’s Climate Prediction Center.

 

How Do El Niño and La Niña Impact Central Kentucky and Southern Indiana Weather?

Affects from El Niño and La Niña tend to be small across the Ohio Valley.  However, moderate and especially strong events do at times affect the region, especially during the mid winter through spring months.  The following graphics depict November through March temperature and precipitation anomalies associated with nine of the strongest El Niño and La Niña episodes.  These composites DO NOT represent a forecast of expected conditions.

 

El Niño

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November-March Temperature Anomalies November-March Precipitation Anomalies

 

These composites DO NOT represent a forecast of expected conditions.  November through March temperature and precipitation anomalies determined from nine of the strongest El Niño episodes since 1950 are shown above.  Warm colors indicate above normal temperatures (left) and below normal precipitation (right), while cool colors indicate below normal temperatures (left) and above normal precipitation (right).  There isn't much of a temperature signal for our area, though we tend toi lean slightly warmer.  There is a better signal for precipitation, as we are often drier than normal during El NiñoImages courtesy of NOAA's Earth System Research Laboratory.

 

La Niña

temp pcpn
November-March Temperature Anomalies November-March Precipitation Anomalies

 

These composites DO NOT represent a forecast of expected conditions.  November through March temperature and precipitation anomalies determined from eight of the strongest La Niña episodes since 1950 are shown above.  Warm colors indicate above normal temperatures (left) and below normal precipitation (right), while cool colors indicate below normal temperatures (left) and above normal precipitation (right).  The Ohio and Tennessee Valleys tend to be warm and wet during LaNiñaImages courtesy of NOAA's Earth System Research Laboratory.

 

El Niño: Risk of Temperature/Precipitation Extremes

The images below depict the odds of extreme wet/dry or warm/cold fall-spring months associated with historical El Niño episodes.  Extreme weather is defined as being in the highest or lowest 20% of the 100 year record.  The climatological average risk of extreme weather any given season is 20%.  These composites DO NOT represent a forecast of expected conditions.

 

El Niño: Risk of Temperature Extremes

temp risk temp risk temp risk Radar/Photo
November - January December - February January - March February - April

 

These composites DO NOT represent a forecast of expected conditions.  The above four images depict the odds of extreme warm or cold fall-spring months associated with past El Niños.  Extreme weather is defined as being in the warmest or coldest 20% of the 100 year record.  The climatological average risk of extreme weather any given season is 20%.  Warm colors indicate an increased risk of warm temperature extremes, while cool colors indicate an increased risk of cold temperature extremes.  El Niño doesn't have much say in how our temperatures end up, though we do tend to have a later start to spring after an El Niño winter.  Click the images to enlarge.  Images courtesy of NOAA's Earth System Research Laboratory.

 

El Niño: Risk of Precipitation Extremes

pcpn risk pcpn risk pcpn risk Radar/Photo
November - January December - February January - March February - April

 

These composites DO NOT represent a forecast of expected conditions.  The above images depict the odds of extreme wet or dry fall-spring months associated with past El Niños.  Extreme weather is defined as being in the wettest or driest 20% of the 100 year record.  The climatological average risk of extreme weather any given season is 20%.  Warm colors indicate an increased risk of dry precipitation extremes, while green colors indicate an increased risk of wet precipitation extremes.  Our region tends to be drier than normal, especially during the mid to late winter.  Click the images to enlarge.  Images courtesy of NOAA's Earth System Research Laboratory.

 

La Niña: Risk of Temperature/Precipitation Extremes

The images below depict the odds of extreme wet/dry or warm/cold fall-spring months associated with historical La Niña episodes.  Extreme weather is defined as being in the highest or lowest 20% of the 100 year record.  The climatological average risk of extreme weather any given season is 20%.  These composites DO NOT represent a forecast of expected conditions.

 

La Niña: Risk of Temperature Extremes

temp risk temp risk temp risk Radar/Photo
November - January December - February January - March February - April

 

These composites DO NOT represent a forecast of expected conditions.  The above images depict the odds of extreme warm or cold fall-spring months associated with past La Niña's. Extreme weather is defined as being in the warmest or coldest 20% of the 100 year record. The climatological verage risk of extreme weather any given season is 20%. Warm colors indicate an increased risk of warm temperature extremes, while cool colors indicate an increased risk of cold temperature extremes. The temperature signal for this area is weak, but we tend to move toward warmer than normal readings. Click the images to enlarge. Images courtesy of NOAA's Earth System Research Laboratory.

 

La Niña: Risk of Precipitation Extremes

temp risk temp risk temp risk Radar/Photo
November - January December - February January - March February - April

 

These composites DO NOT represent a forecast of expected conditions.  The above images depict the odds of extreme wet or dry fall-spring months associated with past La Niña's.  Extreme weather is defined as being in the wettest or driest 20% of the 100 year record.  The climatological average risk of extreme weather any given season is 20%.  Warm colors indicate an increased risk of dry precipitation extremes, while green colors indicate an increased risk of wet precipitation extremes. In the Ohio Valley we tend to have a dry end to fall, a wet winter, and then a slightly drier start to spring.  Click the images to enlarge.  Images courtesy of NOAA's Earth System Research Laboratory.

Official Long-Range Forecasts

Below are official long-range forecasts issued by the Climate Prediction Center (CPC).  Professionals at CPC take into account many different factors when assembling these forecasts, including El Niño/La Niña.

One-Month Forecast

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Chances of Above/Below Normal Temperatures Chances of Above/Below Normal Precipitation

 

Three-Month Forecast

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Chances of Above/Below Normal Temperatures Chances of Above/Below Normal Precipitation

El Niño/La Niña & Spring Severe Thunderstorm Frequency

A paper published in Nature Geoscience in April 2015 examines the influence of El Niño/La Niña on springtime hailstorms and tornadoes across the contiguous United States from late winter through spring.  The images below are adapted from that paper, and show tornado and hail frequencies for the spring months (March-May) during El Niño (left column) and La Niña (right column).  The authors explain that the connection between El Niño/La Niña conditions and summertime storms is less clear, and unfortunately that is the time of year when severe storms peak throughout much of the United States. But for springtime, at least, El Niño/La Niña data may be able to refine seasonal severe weather outlooks.

Tornado and hail frequencies for the spring months (March-May) during El Niño (left column) and La Niña (right column).  Purple favors higher storm event frequency, and brown favors lower storm event frequency.  Specifics vary, but in general, springtime tornadoes and hailstorms are less frequent in the central and southern United States during El Niño, and more frequent during La Niña. Image courtesy of NOAA climate.gov.