ENSO: Recent Evolution,
Current Status and Predictions
Update prepared by:
Climate Prediction Center / NCEP
26 August 2024
Outline
Summary
Recent Evolution and Current Conditions
Oceanic Niño Index (ONI)
Pacific SST Outlook
U.S. Seasonal Precipitation and Temperature Outlooks
Summary
Summary
* Note: These statements are updated once a month (2
nd
Thursday of each month) in association
with the ENSO Diagnostics Discussion, which can be found by clicking here.
ENSO Alert System Status: La Niña Watch
ENSO-neutral conditions are present.*
Equatorial sea surface temperatures (SSTs) are above average in the western
Pacific and near-to-below-average in the eastern Pacific Ocean.
ENSO-neutral is expected to continue for the next several months, with La Niña
favored to emerge during September-November (66% chance) and persist
through the Northern Hemisphere winter 2024-25 (74% chance during
November-January).*
Positive sea surface temperature (SST)
anomalies persisted across most of the
eastern and central Pacific Ocean from
the beginning of the period until April
2024.
Since mid March 2024, below-average
SSTs have emerged in the eastern
Pacific and expanded westward.
Recent Evolution of
Equatorial Pacific SST
Departures (
o
C)
Niño Region SST
Departures (
o
C) Recent
Evolution
The latest weekly
SST departures are:
Niño 4 0.5ºC
Niño 3.4
0.0ºC
Niño 3
-0.2ºC
Niño 1+2
-0.3ºC
SST Departures (
o
C) in the Tropical Pacific During the Last
Four Weeks
In the last four weeks, equatorial SSTs were above average in the western Pacific
Ocean. Near-to-below-average SSTs were evident in the east-central and eastern
Pacific Ocean.
26
30
Global SST Departures (
o
C) During the Last Four Weeks
During the last four weeks, equatorial SSTs were above average across the western Pacific Ocean, around
the Maritime Continent, and in the Indian Ocean. Near-to-below-average SSTs were evident in the east-
central and eastern Pacific Ocean. Equatorial Atlantic SSTs were mostly near average.
26
30
30
Weekly SST Departures
during the Last Four
Weeks
During the last 4 weeks, near-to-below-
average SSTs persisted in the east-central
and eastern Pacific Ocean, while above-
average 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 dominated the east-central
equatorial Pacific Ocean. Positive changes were evident in the far eastern Pacific.
Upper-Ocean Conditions in
the Equatorial Pacific
The basin-wide equatorial upper ocean (0-300 m)
heat content is greatest prior to and during the
early stages of a Pacific warm (El Niño) episode
(compare top 2 panels), and least prior to and
during 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 heat
anomalies (below average) and thermocline
slope index (slightly above average) reflect
ENSO-neutral.
The monthly thermocline slope index represents the
difference in anomalous depth of the 20ºC isotherm
between the western Pacific (160ºE-150ºW) and the
eastern 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. Since the beginning of August 2024, negative
temperature anomalies have weakened.
Sub-Surface Temperature Departures in the Equatorial
Pacific
Most recent pentad analysis
Over the last couple of months, negative subsurface
temperature anomalies have persisted in the eastern
equatorial Pacific Ocean and extended to the surface.
Below-average temperatures remain at depth in the
central Pacific Ocean, with above-average
temperatures near the surface in the western and
central Pacific.
Tropical OLR and Wind
Anomalies During the Last
30 Days
OLR was above-average (suppressed convection
and precipitation) around the Date Line and over
the western Pacific.
Low-level (850-hPa) easterly wind anomalies
were observed over the east-central and
eastern equatorial Pacific Ocean.
Upper-level (200-hPa) wind anomalies were
easterly over the east-central equatorial
Pacific Ocean.
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 eastward-
propagating oceanic Kelvin wave.
Weekly Heat Content
Evolution in the Equatorial
Pacific
Equatorial oceanic Kelvin waves have alternating
warm and cold phases. The warm phase is
indicated by dashed lines. Down-welling and
warming occur in the leading portion of a Kelvin
wave, and up-welling and cooling occur in the
trailing portion.
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.
Recently, below-average subsurface temperatures
weakened in the central Pacific.
Low-level (850-hPa)
Zonal (east-west) Wind
Anomalies (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 of
westerly and easterly wind anomalies was
evident starting in November 2023. Since
early May 2024, this pattern has
weakened.
Since July 2024, easterly wind anomalies
have mostly dominated over the central
and east-central Pacific Ocean, with some
brief periods of westerly wind anomalies.
Westerly Wind Anomalies (orange/red shading)
Easterly Wind Anomalies (blue shading)
Upper-level (200-hPa)
Velocity Potential
Anomalies
Unfavorable for precipitation (brown shading)
Favorable for precipitation (green shading)
Note: Eastward propagation is not necessarily indicative of the Madden-Julian Oscillation (MJO).
From the beginning of the period, regions of
anomalous divergence (green shading) and
convergence (brown shading) were shifting
eastward. Since early May 2024, this
pattern has weakened.
During late June and July 2024, anomalous
divergence was evident over Indonesia and
the western Pacific and anomalous
convergence persisted over the eastern
Pacific.
In the last few weeks, anomalous
convergence shifted eastward from
Indonesia to the eastern Pacific Ocean.
Outgoing Longwave
Radiation (OLR) Anomalies
Drier-than-average Conditions (orange/red shading)
Wetter-than-average Conditions (blue shading)
Through early March 2024, negative OLR
anomalies (more convection) persisted
over the central equatorial Pacific Ocean
From mid-December 2023 through March
2024, OLR anomalies shifted eastward
from the Indian Ocean/Indonesia to the
western Pacific/Date Line.
Since then, OLR has been generally near-
average or below-average over the Date
Line, with the exception of the first half
of July when above-average OLR emerged.
Recently, above-average OLR was
observed over the west-central Pacific.
Oceanic Niño Index (ONI)
The ONI is based on SST departures from average in the Niño 3.4 region, and is a
principal 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 is
described 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 is
using 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. These
anomalies must also be forecasted to persist for 3 consecutive months.
ONI (ºC): Evolution
since 1950
The most recent ONI value (May –
July 2024) is 0.2ºC.
El Niño
La Niña
Neutral
Historical El Niño and La Niña Episodes Based on the
ONI 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 the
threshold 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 whether
features 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
CPC Probabilistic ENSO Outlook
Updated: 8 August 2024
ENSO-neutral is expected to continue for the next several months, with La Niña favored
to emerge during September-November (66% chance) and persist through the Northern
Hemisphere winter 2024-25 (74% chance during November-January).
IRI Pacific Niño 3.4
SST Model Outlook
Figure provided by the International Research
Institute (IRI) for Climate and Society
(updated 19 August 2024).
The majority of dynamical models
indicate a transition to border-
line La Niña around September-
November 2024, while the
average of the statistical models
predicts ENSO-neutral.
SST Outlook: NCEP CFS.v2 Forecast (PDF corrected)
Issued: 26 August 2024
The CFS.v2 ensemble mean (black dashed line) indicates a transition to La Niña
by September-November 2024.
Atmospheric anomalies over
the North Pacific and North
America During the Last 60
Days
1 of 3
During the period, the pattern of temperature
and heights have been variable over the United
States.
2 of 3
Atmospheric anomalies over
the North Pacific and North
America During the Last 60
Days
During the period, the pattern of temperature
and heights have been variable over the United
States.
3 of 3
Atmospheric anomalies over
the North Pacific and North
America During the Last 60
Days
During the period, the pattern of temperature
and heights have been variable over the United
States.
U.S. Temperature and Precipitation Departures During
the Last 30 Days
End Date: 24 August 2024
Percent of Average Precipitation
Temperature Departures (degree C)
1 of 2
U.S. Temperature and Precipitation Departures During
the Last 90 Days
Percent of Average Precipitation Temperature Departures (degree C)
2 of 2
End Date: 24 August 2024
U. S. Seasonal Outlooks
Precipitation Temperature
September– November 2024
The seasonal outlooks combine the effects of long-term trends, soil moisture,
and, when appropriate, ENSO.
Summary
* Note: These statements are updated once a month (2
nd
Thursday of each month) in association
with the ENSO Diagnostics Discussion, which can be found by clicking here.
ENSO Alert System Status: La Niña Watch
ENSO-neutral conditions are present.*
Equatorial sea surface temperatures (SSTs) are above average in the western
Pacific and near-to-below-average in the eastern Pacific Ocean.
ENSO-neutral is expected to continue for the next several months, with La Niña
favored to emerge during September-November (66% chance) and persist
through the Northern Hemisphere winter 2024-25 (74% chance during
November-January).*
