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El Niño 75 Percent Likely to Become La Niña By Fall or Winter, NOAA Says
Brian Donegan
Published: May 12, 2016 The current rapidly weakening El Niño is expected to vanish altogether by summer and has a 75 percent chance of being replaced by its opposite, La Niña, during fall and winter, according to an updated NOAA outlook.
El Niño/La Niña, the periodic warming/cooling of the equatorial eastern and central Pacific Ocean, can shift weather patterns over a period of months, bringing the possibility of more sustained warm, cold, wet, or dry weather in parts of the world.
After tying the record for the strongest El Niño, as defined by a three-month running mean sea-surface temperature anomaly in the so-called Niño 3.4 region of the central and eastern equatorial Pacific Ocean, sea-surface temperatures have accelerated their cooling pace since early February.
(MORE: El Niño 2015-2016 Ties a Record)
Weekly sea-surface temperature (SST) anomalies peaked the week of Nov. 18 at 3.1 degrees Celsius above average, and have now dropped to 0.8 degrees above average as of the week of May 4. Those are values last seen in April 2015, and a drop by half of what was seen in mid-to-late-March, according to NOAA's Climate Prediction Center.
You can see this in recent SST animations, illustrating nicely the peak coverage of large warm anomalies during the northern hemisphere's winter and early spring, followed by a steeper decline in later in February, March and April.
This is the difference in sea surface temperature anomalies between December 2015 and April 2016 in the equatorial Pacific Ocean.
(NOAA)
Looking below the surface, you can also see a trend of colder-than-average water working its way eastward across the International Date Line, eating away at the warmer-than-average equatorial Pacific water from below, another sign of El Niño's future demise.
Central and eastern Pacific Ocean temperature anomalies (degrees Celsius) to a depth of about 450 meters below the surface from early March to early May 2016.
NOAA's May El Niño outlook suggests this El Niño may vanish by early summer.
In fact, the large majority of model forecasts suggest the equatorial waters may become cooler than average this summer, potentially even swinging into La Niña as early as this fall. A few ensemble forecasts even have a strong La Niña forecasted by late summer or fall.
Ensemble model forecasts of SST anomalies in the Niño 3.4 region from April to December 2016, showing the potential La Niña developing by summer 2016.
Both NOAA's Climate Prediction Center and Australia's Bureau of Meteorology issued a "La Niña watch," indicating La Niña may develop within the next 6 months.
NOAA/CPC places the odds of La Niña conditions by late summer at over 60 percent, increasing to over a 75 percent likelihood by late fall.
El Niño and La Niña events typically only last for 9-12 months, and typically recur again every 2-7 years, according to Columbia University's International Research Institute for Climate and Society.
(MORE: A Tale of Two El Niños...What Made This One Different?)
Flip-flops from a strong El Niño to La Niña are not unusual.
Following the record strong El Niño of 1997-98, La Niña almost immediately set in the following summer, reaching moderate-to-strong intensity before finally ending in spring 2001.
A similar thing happened following the strong El Niño of 1972-73.
However, neutral conditions followed three other strong El Niños of 1982-83, 1965-66 and 1957-58.
What Does It Mean for Your Forecast?
Summer 2016
There are some broad trends that have shown up in past weakening El Niño events that could give a hint on what to expect this summer.
(MORE: Summer Outlook 2016)
"If we look at rapidly decaying historical ENSO events (trends, instead of actual values), we see that the summer heat is centered in the northern Plains into the Great Lakes states," said Dr. Todd Crawford, chief meteorologist at The Weather Company's energy division.
A summer 2016 temperature outlook, issued in mid-March 2016, by The Weather Company Professional Division
Atlantic Hurricane Season 2016
Strengthening El Niños during the Atlantic hurricane season tend to yield stronger wind shear,
which tends to either tear apart developing or mature tropical cyclones.
Sure enough, June through October 2015 Caribbean wind shear was the highest on record dating to 1979, according to Dr. Phil Klotzbach, tropical scientist at Colorado State University.
<center> </center>
Klotzbach also found that the chance of a U.S. hurricane impact rises dramatically in a La Niña or neutral (neither El Niño or La Niña) season compared to an El Niño season.
<center> </center>
With El Niño increasingly likely to vanish by the start of the 2016 season, it at least loads the dice a bit toward an increased chance of tropical cyclones surviving into the Caribbean Sea, or forming there, particularly later in the season as El Niño disappears farther in the rear-view mirror.
If El Niño was the only factor, that is.
The odds may shift a bit toward a more active Atlantic hurricane season in 2016, but El Niño's absence doesn't guarantee that outcome.
As we wrote in January 2016, prior hurricane seasons after strong El Niños have produced anywhere from only four named storms (1983) to 14 named storms (1998), three hurricanes (1983) to 10 hurricanes (1998).
This fizzling El Niño also doesn't mean the season poses any greater threat to the U.S. compared to any other year, as landfalls tend to be poorly correlated with numbers of named storms.
(MORE: 2016 Atlantic Hurricane Season Outlook)
Winter 2016-2017
We've said many times an El Niño, La Niña, or the lack of either, known as the neutral phase, is only one large-scale forcing on the atmosphere. It is not the be-all and end-all determining whether a season is wet, dry, cold or warm.
Despite that, the peak atmospheric reponse to the equatorial Pacific anomalies tends to occur in the northern hemisphere winter months.
So, in the event we have a La Niña settling in by fall or winter, let's take a look at December-February U.S. temperature and precipitation anomalies during weak (SST anomalies from 0.5 to 0.9 degrees below average), moderate (1.0 to 1.4 degrees below average) and strong (1.5 degrees below average or cooler) La Niñas.
Temperatures
While there are some differences among La Niña magnitudes, some commonalities emerge regarding La Niña winter forcing in the U.S.:
December-February temperature anomalies (degrees Fahrenheit) during 11 weak, 6 moderate, and 3 strong La Niña events dating to 1950, using the classification scheme from Jan Null.
Precipitation
Again, despite some differences among La Niña magnitudes, some commonalities are apparent:
December-February precipitation anomalies (inches) during 11 weak, 6 moderate, and 3 strong La Niña events dating to 1950, using the classification scheme from Jan Null.
El Niño 75 Percent Likely to Become La Niña By Fall or Winter, NOAA Says
Brian Donegan
Published: May 12, 2016 The current rapidly weakening El Niño is expected to vanish altogether by summer and has a 75 percent chance of being replaced by its opposite, La Niña, during fall and winter, according to an updated NOAA outlook.
El Niño/La Niña, the periodic warming/cooling of the equatorial eastern and central Pacific Ocean, can shift weather patterns over a period of months, bringing the possibility of more sustained warm, cold, wet, or dry weather in parts of the world.
After tying the record for the strongest El Niño, as defined by a three-month running mean sea-surface temperature anomaly in the so-called Niño 3.4 region of the central and eastern equatorial Pacific Ocean, sea-surface temperatures have accelerated their cooling pace since early February.
(MORE: El Niño 2015-2016 Ties a Record)
Weekly sea-surface temperature (SST) anomalies peaked the week of Nov. 18 at 3.1 degrees Celsius above average, and have now dropped to 0.8 degrees above average as of the week of May 4. Those are values last seen in April 2015, and a drop by half of what was seen in mid-to-late-March, according to NOAA's Climate Prediction Center.
You can see this in recent SST animations, illustrating nicely the peak coverage of large warm anomalies during the northern hemisphere's winter and early spring, followed by a steeper decline in later in February, March and April.
(NOAA)
Looking below the surface, you can also see a trend of colder-than-average water working its way eastward across the International Date Line, eating away at the warmer-than-average equatorial Pacific water from below, another sign of El Niño's future demise.
NOAA's May El Niño outlook suggests this El Niño may vanish by early summer.
In fact, the large majority of model forecasts suggest the equatorial waters may become cooler than average this summer, potentially even swinging into La Niña as early as this fall. A few ensemble forecasts even have a strong La Niña forecasted by late summer or fall.
Both NOAA's Climate Prediction Center and Australia's Bureau of Meteorology issued a "La Niña watch," indicating La Niña may develop within the next 6 months.
NOAA/CPC places the odds of La Niña conditions by late summer at over 60 percent, increasing to over a 75 percent likelihood by late fall.
El Niño and La Niña events typically only last for 9-12 months, and typically recur again every 2-7 years, according to Columbia University's International Research Institute for Climate and Society.
(MORE: A Tale of Two El Niños...What Made This One Different?)
Flip-flops from a strong El Niño to La Niña are not unusual.
Following the record strong El Niño of 1997-98, La Niña almost immediately set in the following summer, reaching moderate-to-strong intensity before finally ending in spring 2001.
A similar thing happened following the strong El Niño of 1972-73.
However, neutral conditions followed three other strong El Niños of 1982-83, 1965-66 and 1957-58.
What Does It Mean for Your Forecast?
Summer 2016
There are some broad trends that have shown up in past weakening El Niño events that could give a hint on what to expect this summer.
(MORE: Summer Outlook 2016)
"If we look at rapidly decaying historical ENSO events (trends, instead of actual values), we see that the summer heat is centered in the northern Plains into the Great Lakes states," said Dr. Todd Crawford, chief meteorologist at The Weather Company's energy division.
Atlantic Hurricane Season 2016
Strengthening El Niños during the Atlantic hurricane season tend to yield stronger wind shear,
which tends to either tear apart developing or mature tropical cyclones.
Sure enough, June through October 2015 Caribbean wind shear was the highest on record dating to 1979, according to Dr. Phil Klotzbach, tropical scientist at Colorado State University.
<center> </center>
Klotzbach also found that the chance of a U.S. hurricane impact rises dramatically in a La Niña or neutral (neither El Niño or La Niña) season compared to an El Niño season.
<center> </center>
With El Niño increasingly likely to vanish by the start of the 2016 season, it at least loads the dice a bit toward an increased chance of tropical cyclones surviving into the Caribbean Sea, or forming there, particularly later in the season as El Niño disappears farther in the rear-view mirror.
If El Niño was the only factor, that is.
The odds may shift a bit toward a more active Atlantic hurricane season in 2016, but El Niño's absence doesn't guarantee that outcome.
As we wrote in January 2016, prior hurricane seasons after strong El Niños have produced anywhere from only four named storms (1983) to 14 named storms (1998), three hurricanes (1983) to 10 hurricanes (1998).
This fizzling El Niño also doesn't mean the season poses any greater threat to the U.S. compared to any other year, as landfalls tend to be poorly correlated with numbers of named storms.
(MORE: 2016 Atlantic Hurricane Season Outlook)
Winter 2016-2017
We've said many times an El Niño, La Niña, or the lack of either, known as the neutral phase, is only one large-scale forcing on the atmosphere. It is not the be-all and end-all determining whether a season is wet, dry, cold or warm.
Despite that, the peak atmospheric reponse to the equatorial Pacific anomalies tends to occur in the northern hemisphere winter months.
So, in the event we have a La Niña settling in by fall or winter, let's take a look at December-February U.S. temperature and precipitation anomalies during weak (SST anomalies from 0.5 to 0.9 degrees below average), moderate (1.0 to 1.4 degrees below average) and strong (1.5 degrees below average or cooler) La Niñas.
Temperatures
While there are some differences among La Niña magnitudes, some commonalities emerge regarding La Niña winter forcing in the U.S.:
- Cold: Northern Plains, Upper Midwest, New England, New York state, West Coast
- Warm: Southern Plains, Southeast
Precipitation
Again, despite some differences among La Niña magnitudes, some commonalities are apparent:
- Wet: Pacific Northwest, Bitterroots (western Montana/Idaho), parts of the Ohio Valley, Tennessee Valley
- Dry: Southern Plains, Gulf/Southeast coast including Florida, Southern California, Desert Southwest
