ENSO: Recent Evolution,
Current Status and Predictions

Update prepared by:
Climate Prediction Center / NCEP
16 September 2024

Outline
Summary
Recent Evolution and Current Conditions
Oceanic Niño Index (ONI)

Pacific SST Outlook
U.S. Seasonal Precipitation and Temperature Outlooks
SummarySummary
ENSO Alert System Status: La Niña Watch
ENSO-neutral conditions are present.*
Equatorial sea surface temperatures (SSTs) are near-to-below-average in thecentral and eastern Pacific Ocean.
La Niña favored to emerge in September-November (71% chance) and is
expected to persist through January-March 2025.** Note: These statements are updated once a month (2nd Thursday of each month) in association
with the ENSO Diagnostics Discussion, which can be found by clicking here.

Recent Evolution ofEquatorial Pacific SST
Departures (oC)
Positive sea surface temperature (SST)
anomalies persisted across most of theeastern and central Pacific Ocean fromthe beginning of the period until April
2024.
Since mid-March 2024, near-to-belowaverage SSTs have emerged in theeastern Pacific and expandedwestward.

Niño Region SST
Departures (oC) RecentEvolutionThe latest weekly
SST departures are:Niño 4
Niño 3.4
Niño 3
Niño 1+2

0.1ºC-0.2ºC-0.2ºC-0.2ºCSST Departures (oC) in the Tropical Pacific During the Last
Four Weeks
In the last four weeks, equatorial SSTs were above average in the western PacificOcean. Near-to-below-average SSTs were evident in the east-central and eastern
Pacific Ocean.

2630

Global SST Departures (oC) During the Last Four Weeks
During the last four weeks, equatorial SSTs were above average across the western Pacific Ocean, aroundthe Maritime Continent, the Indian Ocean, and most of the Atlantic Ocean. Near-to-below-average SSTs
were evident in the east-central and eastern Pacific Ocean.

302630Weekly SST Departuresduring the Last Four
Weeks

During the last 4 weeks, near-to-belowaverage SSTs persisted in the east-central
and eastern Pacific Ocean, while aboveaverage SSTs persisted in the western
Pacific.

Change in Weekly SST Departures over the Last Four
Weeks
During the last four weeks, negative SST anomaly changes prevailed across the westernand central equatorial Pacific Ocean.

Upper-Ocean Conditions in
the Equatorial Pacific

The basin-wide equatorial upper ocean (0-300 m)heat content is greatest prior to and during theearly stages of a Pacific warm (El Niño) episode(compare top 2 panels), and least prior to andduring the early stages of a cold (La Niña)
episode.
The slope of the oceanic thermocline is least(greatest) during warm (cold) episodes.
Recent values of the upper-ocean heatanomalies (below average) and thermocline
slope index (slightly above average) reflect
ENSO-neutral.
The monthly thermocline slope index represents thedifference in anomalous depth of the 20ºC isotherm
between the western Pacific (160ºE-150ºW) and theeastern Pacific (90º-140ºW).

Central and Eastern Pacific Upper-Ocean (0-300 m)
Weekly Average Temperature Anomalies
Positive subsurface temperature anomalies persisted through mid-January 2024. Starting in November
2023, positive subsurface temperature anomalies weakened to near zero. Negative temperature
anomalies have dominated since February 2024. In the last couple of weeks, negative temperature
anomalies have strengthened.

Sub-Surface Temperature Departures in the EquatorialPacificOver the last couple of months, negative subsurface
temperature anomalies have persisted in the easternequatorial Pacific Ocean and extended to the surface.

Most recent pentad analysis
Below-average temperatures remain at depth in thecentral Pacific Ocean, while above-averagetemperatures prevail near the surface in thewestern Pacific.

Tropical OLR and Wind
Anomalies During the Last
30 Days
OLR was below average (enhanced convection andprecipitation) near the equator in the westernPacific.

Low-level (850-hPa) easterly wind anomalies
were observed across most of the equatorial
Pacific Ocean.

Upper-level (200-hPa) wind anomalies werecross-equatorial, with a westerly trajectory,over the eastern equatorial Pacific Ocean,
while anomalies were westerly over the DateLine.

Intraseasonal Variability

Intraseasonal variability in the atmosphere (wind and pressure), which is often related
to the Madden-Julian Oscillation (MJO), can significantly impact surface and subsurface
conditions across the Pacific Ocean.

Related to this activity:
Significant weakening of the low-level easterly winds usually initiates an eastwardpropagating oceanic Kelvin wave.

Weekly Heat Content
Evolution in the Equatorial
Pacific
Significant equatorial oceanic Kelvin wave activity(dashed and dotted lines) has been present
throughout the period shown.
Through January 2024, above-average subsurface
temperatures persisted across most of the Pacific
Ocean.
Upwelling Kelvin waves were observed during
December 2023, May 2024, and July 2024.
Since late August 2024, below-average subsurface
temperatures strengthened in the eastern andcentral Pacific.
Equatorial oceanic Kelvin waves have alternating
warm and cold phases. The warm phase isindicated by dashed lines. Down-welling andwarming occur in the leading portion of a Kelvinwave, and up-welling and cooling occur in thetrailing portion.

Low-level (850-hPa)
Zonal (east-west) WindAnomalies (m s-1)
At times, the Madden Julian-Oscillation(MJO) has contributed to the eastward
propagation of low-level wind anomalies.
An eastward propagating pattern ofwesterly and easterly wind anomalies wasevident starting in November 2023. Since
early May 2024, this pattern hasweakened.

Since July 2024, easterly wind anomalies
have mostly dominated over the central
and east-central Pacific Ocean, with somebrief periods of westerly wind anomalies.

Westerly Wind Anomalies (orange/red shading)Easterly Wind Anomalies (blue shading)Upper-level (200-hPa)
Velocity PotentialAnomalies
From the beginning of the period, regions ofanomalous divergence (green shading) andconvergence (brown shading) were shifting
eastward. This pattern has weakened in May
2024.
During most of July and since mid-August
2024, anomalous divergence was evident
over Indonesia and the western Pacific andanomalous convergence persisted over theeastern Pacific.

Unfavorable for precipitation (brown shading)Favorable for precipitation (green shading)Note: Eastward propagation is not necessarily indicative of the Madden-Julian Oscillation (MJO).

Outgoing Longwave
Radiation (OLR) Anomalies
Since mid-March 2024 positive OLR
anomalies (suppressed convection/rainfall)
have periodically emerged near the DateLine.
Since late August 2024, negative OLR
anomalies (enhanced convection/rainfall)
have persisted near Indonesia and thewestern Pacific Ocean.

Drier-than-average Conditions (orange/red shading)
Wetter-than-average Conditions (blue shading)Oceanic Niño Index (ONI)The ONI is based on SST departures from average in the Niño 3.4 region, and is aprincipal measure for monitoring, assessing, and predicting ENSO.
Defined as the three-month running-mean SST departures in the Niño 3.4 region.
Departures are based on a set of improved homogeneous historical SST analyses(Extended Reconstructed SST – ERSST.v5). The SST reconstruction methodology isdescribed in Huang et al., 2017, J. Climate, vol. 30, 8179-8205.)
It is one index that helps to place current events into a historical perspective.

Note: a different SST dataset is used for weekly SST monitoring (slides #4-9) and isusing OISSTv2.1 (Huang et al., 2021).

NOAA Operational Definitions for El Niño and La Niña

El Niño: characterized by a positive ONI greater than or equal to +0.5ºC.
La Niña: characterized by a negative ONI less than or equal to -0.5ºC.
By historical standards, to be classified as a full-fledged El Niño or La Niña episode,these thresholds must be exceeded for a period of at least 5 consecutive overlapping
3-month seasons.

CPC considers El Niño or La Niña conditions to occur when the monthly Niño3.4 OISST
departures meet or exceed +/- 0.5ºC along with consistent atmospheric features. Theseanomalies must also be forecasted to persist for 3 consecutive months.

ONI (ºC): Evolution
since 1950

The most recent ONI value (June –August 2024) is 0.1ºC.

El Niño
Neutral

La NiñaHistorical El Niño and La Niña Episodes Based on theONI computed using ERSST.v5
Recent Pacific warm (red) and cold (blue) periods based on a threshold of +/- 0.5 ºC for the Oceanic
Nino Index (ONI) [3 month running mean of ERSST.v5 SST anomalies in the Nino 3.4 region (5N-5S, 120-170W)].
For historical purposes, periods of below and above normal SSTs are colored in blue and red when thethreshold is met for a minimum of 5 consecutive over-lapping seasons.
The ONI is one measure of the El Niño-Southern Oscillation, and other indices can confirm whetherfeatures consistent with a coupled ocean-atmosphere phenomenon accompanied these periods. The complete
table going back to DJF 1950 can be found here.
Year

DJF

JFM

FMA

MAM

AMJ

MJJ

JJA

JAS

ASO

SON

OND

NDJ

2012

-0.9

-0.7

-0.6

-0.5

-0.3

0.0

0.2

0.4

0.4

0.3

0.1

-0.2

2013

-0.4

-0.4

-0.3

-0.3

-0.4

-0.4

-0.4

-0.3

-0.3

-0.2

-0.2

-0.3

2014

-0.4

-0.5

-0.3

0.0

0.2

0.2

0.0

0.1

0.2

0.5

0.6

0.7

2015

0.5

0.5

0.5

0.7

0.9

1.2

1.5

1.9

2.2

2.4

2.6

2.6

2016

2.5

2.1

1.6

0.9

0.4

-0.1

-0.4

-0.5

-0.6

-0.7

-0.7

-0.6

2017

-0.3

-0.2

0.1

0.2

0.3

0.3

0.1

-0.1

-0.4

-0.7

-0.8

-1.0

2018

-0.9

-0.9

-0.7

-0.5

-0.2

0.0

0.1

0.2

0.5

0.8

0.9

0.8

2019

0.7

0.7

0.7

0.7

0.5

0.5

0.3

0.1

0.2

0.3

0.5

0.5

2020

0.5

0.5

0.4

0.2

-0.1

-0.3

-0.4

-0.6

-0.9

-1.2

-1.3

-1.2

2021

-1.0

-0.9

-0.8

-0.7

-0.5-0.4

-0.4

-0.5

-0.7

-0.8

-1.0

-1.0

2022

-1.0

-0.9

-1.0

-1.1

-1.0

-0.9

-0.8

-0.9

-1.0

-1.0

-0.9

-0.8

2023

-0.7

-0.4

-0.1

0.2

0.5

0.8

1.1

1.3

1.6

1.8

1.9

2.0

2024

1.8

1.5

1.1

0.7

0.4

0.2

0.1

CPC Probabilistic ENSO Outlook
Updated: 12 September 2024
La Niña favored to emerge during September-November (71% chance) and persist
through January-March 2025.

IRI Pacific Niño 3.4
SST Model Outlook

The majority of dynamical models
indicate a transition to borderline La Niña around SeptemberNovember 2024, while theaverage of the statistical models
predicts ENSO-neutral.

Figure provided by the International ResearchInstitute (IRI) for Climate and Society(updated 19 August 2024).

SST Outlook: NCEP CFS.v2 Forecast (PDF corrected)
Issued: 16 September 2024
The CFS.v2 ensemble mean (black dashed line) indicates a transition to La Niña
in October 2024 and persisting through January-March 2025.

Atmospheric anomalies overthe North Pacific and North
America During the Last 60Days
With the exception of the second half of August,above-average heights and temperatures haveprevailed over the western U.S.
Over the eastern U.S., temperature anomalies
have been relatively cooler.

1 of 3

Atmospheric anomalies over
the North Pacific and North
America During the Last 60
Days
With the exception of the second half of August,above-average heights and temperatures haveprevailed over the western U.S.
Over the eastern U.S., temperature anomalies
have been relatively cooler.

2 of 3

Atmospheric anomalies over
the North Pacific and North
America During the Last 60
Days
With the exception of the second half of August,above-average heights and temperatures haveprevailed over the western U.S.
Over the eastern U.S., temperature anomalies
have been relatively cooler.

3 of 3

U.S. Temperature and Precipitation Departures During
the Last 30 Days

End Date: 14 September 2024
Percent of Average Precipitation

Temperature Departures (degree C)

1 of 2

U.S. Temperature and Precipitation Departures During
the Last 90 Days

End Date: 14 September 2024
Percent of Average Precipitation

Temperature Departures (degree C)

2 of 2

U. S. Seasonal Outlooks
September– November 2024
The seasonal outlooks combine the effects of long-term trends, soil moisture,and, when appropriate, ENSO.
Precipitation

TemperatureSummaryENSO Alert System Status: La Niña Watch
ENSO-neutral conditions are present.*
Equatorial sea surface temperatures (SSTs) are near-to-below-average in thecentral and eastern Pacific Ocean.
La Niña favored to emerge in September-November (71% chance) and is
expected to persist through January-March 2025.** Note: These statements are updated once a month (2nd Thursday of each month) in association
with the ENSO Diagnostics Discussion, which can be found by clicking here.