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2014 September Quick Look

Published: September 18, 2014

A monthly summary of the status of El Niño, La Niña, and the Southern Oscillation, or ENSO, based on the NINO3.4 index (120-170W, 5S-5N)

During August through early September the observed ENSO conditions moved to those of a borderline El Niño. Most of the ENSO prediction models indicate weak El Niño conditions during the September-November season in progress, strengthening slightly and peaking at weak strength during winter 2014-15 and lasting into the first few months of 2015.

Figures 1 ((the official CPC ENSO probability forecast) and 3 (the objective model-based IRI ENSO probability forecast) are often quite similar. However, occasionally they may differ noticeably. There can be several possible reasons for differences. One is the human forecasters, using their experience and judgment, may disagree to some degree with the models, which may have known biases. Another reason is the models are not run at the same time that the forecasters make their assessment, so that the starting ENSO conditions may be slightly different between the two times. The charts on this Quick Look page are updated at two different times of the month, typically about a week apart, with the IRI forecast run later. Also note that the CPC forecast starts on the previous season while the IRI forecast starts on the current season.
Click on the for more information on each figure.

Historically Speaking

    El Niño and La Niña events tend to develop during the period Apr-Jun and they
  • Tend to reach their maximum strength during October - February
  • Typically persist for 9-12 months, though occasionally persisting for up to 2 years
  • Typically recur every 2 to 7 years

ENSO Forecast

CPC ENSO Update

Published: September 4, 2014

El Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued by the Climate Prediction Center/NCEP/NWS

ENSO Alert System Status: El Niño Watch

Synopsis: The chance of El Niño is at 60-65% during the Northern Hemisphere fall and winter.

During August 2014, above-average sea surface temperatures (SST) continued across much of the equatorial Pacific (Figure 1). Most of the Niño indices warmed during the month with values of +0.5°C in Niño-4, +0.4°C in Niño-3.4, +0.4°C in Niño-3, and +0.8°C in Niño-1+2 (Figure 2). Subsurface heat content anomalies (averaged between 180º-100ºW) also increased during the month (Figure 3) as above-average subsurface temperatures developed across the central and east-central equatorial Pacific (Figure 4). This warming is associated with the downwelling phase of an equatorial oceanic Kelvin wave triggered in July by low-level westerly wind anomalies. Westerly wind anomalies continued in the central and eastern part of the basin early in August, but weakened by the end of the month. Enhanced easterly upper-level wind anomalies have prevailed during much of the month, and the Southern Oscillation Index has been negative. However, convective cloudiness remained generally near average over most of the region, except for below average cloudiness observed across the central and western Pacific (Figure 5). The lack of a coherent atmospheric El Niño pattern and near-average SSTs in the central Pacific indicate a continuation of ENSO-neutral.

Most of the models continue to predict El Niño to develop during September-November and to continue into early 2015 (Figure 6). A majority of models and the multi-model averages favor a weak El Niño. At this time, the consensus of forecasters expects El Niño to emerge during September-October and to peak at weak strength during the late fall and early winter (3-month values of the Niño-3.4 index between 0.5°C and 0.9°C). The chance of El Niño is at 60-65% during the Northern Hemisphere fall and winter (click CPC/IRI consensus forecast for the chance of each outcome).

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts are also updated monthly in the Forecast Forum section of CPC’s Climate Diagnostics Bulletin. Additional perspectives and analysis are also available in an ENSO blog.

The next ENSO Diagnostics Discussion is scheduled for 9 October 2014. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send an e-mail message to: ncep.list.enso-update@noaa.gov.

NOAA?CPC ENSO Forecast Image

CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
ASO 2014 ~0% 57% 43%
SON 2014 ~0% 45% 55%
OND 2014 1% 38% 61%
NDJ 2014 1% 34% 65%
DJF 2014 2% 34% 64%
JFM 2015 3% 36% 61%
FMA 2015 3% 41% 56%
MAM 2015 4% 48% 48%
AMJ 2015 5% 53% 42%

IRI ENSO Forecast

IRI Technical ENSO Update and Model-Based Probabilistic ENSO Forecast

Published: September 18, 2014

Recent and Current Conditions

The SST anomaly in the NINO3.4 region in recent weeks has returned to a borderline El Niño level, after having retreated to neutral readings during July and August. For August the NINO3.4 SST anomaly was 0.20 C, indicative of neutral conditions, and for Jun-Aug it was 0.28 C. The IRI’s definition of El Niño, like NOAA/Climate Prediction Center’s, requires that the SST anomaly in the Nino3.4 region (5S-5N; 170W-120W) exceed 0.5 C. Similarly, for La Niña, the anomaly must be -0.5 C or less. The climatological probabilities for La Niña, neutral, and El Niño conditions vary seasonally, and are shown in a table at the bottom of this page for each 3-month season. The most recent weekly SST anomaly in the Nino3.4 region was 0.5 C, slightly higher than the 0.20 C observed in August. Although the SST had been near the borderline of weak El Niño conditions in May and June, the atmospheric participation in an El Niño-like pattern had been weak or absent. During September so far, both ocean and atmosphere have been suggestive of weak El Niño conditions, and this situation may finally lead toward a sustained weak El Niño event during the coming several months.

Expected Conditions

What is the outlook for the ENSO status going forward? The most recent official diagnosis and outlook was issued earlier this month in the NOAA/Climate Prediction Center ENSO Diagnostic Discussion, produced jointly by CPC and IRI; it called for a likelihood for a transition from neutral ENSO conditions to El Niño conditions during the early fall 2014 now beginning, with probabilities of El Niño rising to 65% for Nov-Jan 2014-15. The latest set of model ENSO predictions, from mid-September, now available in the IRI/CPC ENSO prediction plume, is discussed below. Currently, Nino3.4 SST anomalies are back to borderline El Niño level after having retreated during July and August, following borderline El Niño levels being observed during May and June. Subsurface temperature anomalies across the eastern equatorial Pacific have risen during the last month, after having subsided to near average during the previous two months, after being much above average during spring.  In the atmosphere, the basin-wide sea level pressure pattern (e.g. the SOI) has recently reached borderline to weak El Niño level (i.e., a negative SOI), and weak anomalous low-level westerlies and have also appeared. Upper level anomalous westerlies have been observed more steadily in the last couple of months. Anomalous convection (as measured by OLR) has been near average east of the dateline, suppressed near and just west of the dateline, and enhanced in part of the far western tropical Pacific.  With the exception of the convection pattern, the recent atmospheric conditions are suggestive of weak El Niño. Together, the oceanic and atmospheric features reflect a warm-neutral to a borderline or weak El Niño condition.

As of mid-September, none of the dynamical or statistical models models predicts La Niña SST conditions for the initial Sep-Nov 2014 season, 58% predicts El Niño conditions, and 42% indicates neutral ENSO. At lead times of 3 or more months into the future, statistical and dynamical models that incorporate information about the ocean’s observed subsurface thermal structure generally exhibit higher predictive skill than those that do not. For the Dec-Feb 2014-15 season, among models that do use subsurface temperature information, 32% predicts ENSO-neutral SSTs, 68% predicts El Niño conditions and none predicts La Niña conditions. For all model types, the probability for neutral ENSO conditions is 40% or below between Oct-Dec 2014 and Mar-May 2015. Probabilities for El Niño rise to more than 60% or more between these same two seasons, peaking at 72% for Jan-Mar 2015. No model predicts La Niña conditions for any of the 3-month periods between Aug-Oct 2014 and Apr-Jun 2015.

Note  – Only models that produce a new ENSO prediction every month are included in the above statement.

Caution is advised in interpreting the distribution of model predictions as the actual probabilities. At longer leads, the skill of the models degrades, and skill uncertainty must be convolved with the uncertainties from initial conditions and differing model physics, leading to more climatological probabilities in the long-lead ENSO Outlook than might be suggested by the suite of models. Furthermore, the expected skill of one model versus another has not been established using uniform validation procedures, which may cause a difference in the true probability distribution from that taken verbatim from the raw model predictions.

An alternative way to assess the probabilities of the three possible ENSO conditions is more quantitatively precise and less vulnerable to sampling errors than the categorical tallying method used above. This alternative method uses the mean of the predictions of all models on the plume, equally weighted, and constructs a standard error function centered on that mean. The standard error is Gaussian in shape, and has its width determined by an estimate of overall expected model skill for the season of the year and the lead time. Higher skill results in a relatively narrower error distribution, while low skill results in an error distribution with width approaching that of the historical observed distribution. This method shows probabilities for La Niña near 0% from Sep-Nov 2014 through Feb-Apr 2015, rising to 7% by May-Jul.  Model probabilities for neutral ENSO conditions are 44% for the initial period of Sep-Nov 2014, 33% for the next running period of Oct-Dec, reach a low of 28% for Nov-Jan through Jan-Mar 2014-15 and rise to 44% by Mar-May 2015. Probabilities for El Niño are 56% for Sep-Nov 2014, rise to 72% for Nov-Jan through Jan-Mar 2014-15, and decline slowly to 49% for May-Jul 2015. The models collectively favor El Niño over other ENSO conditions by a sizable margin between Oct-Dec 2014 and Mar-May 2015.   A plot of the probabilities generated from this most recent IRI/CPC ENSO prediction plume using the multi-model mean and the Gaussian standard error method summarizes the model consensus out to about 10 months into the future. The same cautions mentioned above for the distributional count of model predictions apply to this Gaussian standard error method of inferring probabilities, due to differing model biases and skills. In particular, this approach considers only the mean of the predictions, and not the total range across the models, nor the ensemble range within individual models.

The probabilities derived from the models on the IRI/CPC plume describe, on average, a likely development of El Niño development during the Sep-Nov 2014 season currently in progress, becoming even more likely by Oct-Dec. The consensus of model predictions calls for a weak El Niño event, although a moderate event or no event are also possible. A strong event appears least likely. A caution regarding this latest set of model-based ENSO plume predictions, is that factors such as known specific model biases and recent changes that the models may have missed will be taken into account in the next official outlook to be generated and issued in early October by CPC and IRI, which will include some human judgement in combination with the model guidance.

 

 

Climatological Probabilities
Season La Niña Neutral El Niño
DJF 37% 28% 35%
JFM 34% 37% 29%
FMA 30% 48% 22%
MAM 26% 54% 20%
AMJ 24% 54% 22%
MJJ 25% 51% 24%
JJA 25% 50% 25%
JAS 27% 46% 27%
ASO 29% 40% 31%
SON 32% 34% 34%
OND 34% 31% 35%
NDJ 37% 27% 36%

 

IRI ENSO Forecast Histogram Image

IRI/CPC Mid-Month Plume-Based ENSO Forecast Probabilities

Season La Niña Neutral El Niño
SON 2014 ~0% 44% 56%
OND 2014 ~0% 33% 67%
NDJ 2014 ~0% 28% 72%
DJF 2014 ~0% 28% 72%
JFM 2015 ~0% 28% 72%
FMA 2015 ~0% 35% 65%
MAM 2015 1% 40% 59%
AMJ 2015 4% 43% 53%
MJJ 2015 7% 44% 49%

ENSO Forecast

IRI ENSO Predictions Plume

Published: September 18, 2014

Note on interpreting model forecasts

The following graph and table show forecasts made by dynamical and statistical models for SST in the Nino 3.4 region for nine overlapping 3-month periods. Note that the expected skills of the models, based on historical performance, are not equal to one another. The skills also generally decrease as the lead time increases. Thirdly, forecasts made at some times of the year generally have higher skill than forecasts made at other times of the year--namely, they are better when made between June and December than when they are made between February and May. Differences among the forecasts of the models reflect both differences in model design, and actual uncertainty in the forecast of the possible future SST scenario.

Interactive Chart

You can highlight a specific model by hovering over it either on the chart or the legend. Selecting An item on the legend will toggle the visibility of the model on the page. You can also select DYN MODELS or STAT MODELS to toggle them all at once. Clicking on the "burger" menu above the legend will give you options to download the image or expand to full screen. If you have any feedback on this new feature, please let us know at webmaster@iri.columbia.edu.

List of Models Used

Forecast SST Anomalies (deg C) in the Nino 3.4 Region

Seasons (2014-2015)
Model SON OND NDJ DJF JFM FMA MAM AMJ MJJ
Dynamical models
NCEP CFS version 2 0.6 0.8 0.8 0.8 0.8 0.8 0.9 0.9
NASA GMAO model 0.8 0.9 1 1 1 1 0.9
Japan Met. Agency model 0.5 0.6 0.7 0.8 0.8
Scripps Inst. HCM 0.9 1 1.1 1.1 1.1 1 0.8 0.6 0.5
Lamont-Doherty model 0.2 0.1 0.1 0.1 0.2 0.3 0.4 0.6 0.9
POAMA (Austr) model 0.3 0.3 0.4 0.4 0.4 0.4 0.5
ECMWF model 0.7 0.8 0.9 0.9 0.8
UKMO model 0.4 0.3 0.2 0
KMA (Korea) SNU model 0.8 0.9 0.9 1 1 0.9 0.9 0.8 0.7
ESSIC Intermed. Coupled model 0.4 0.3 0.3 0.2 0.1 0 -0.1 -0.2 -0.4
COLA CCSM3 model 0.9 1.2 1.3 1.4 1.5 1.6 1.4 1 0.6
MÉTÉO FRANCE model 0.8 0.8 0.8 0.8 0.8
CSIR-IRI 3-model MME 0.6 0.8 1 1.1 1 0.8
GFDL CM2.1 Coupled Climate model 0.7 0.9 1 1.1 1.2 1.3 1.3 1.4 1.5
Canadian Coupled Fcst Sys 0.5 0.6 0.7 0.8 0.8 0.8 0.7 0.7 0.8
GFDL CM2.5 FLOR Coupled Climate model 0.6 0.7 0.8 0.9 1.1 1.2 1.3 1.2 1.1
Average, dynamical models 0.6 0.7 0.7 0.8 0.8 0.8 0.8 0.8 0.7
Statistical models
NCEP/CPC Markov model 0.5 0.6 0.8 0.8 0.8 0.7 0.7 0.6 0.5
NOAA/CDC Linear Inverse 0.2 0.2 0.1 0.1 0 0 -0.1 -0.1 -0.1
NCEP/CPC Constructed Analog 0.6 0.9 1 1 1 0.8 0.7 0.5 0.4
NCEP/CPC Can Cor Anal 1.1 1.2 1.2 1 0.8 0.7 0.6 0.5 0.3
Landsea/Knaff CLIPER 0.4 0.5 0.6 0.7 0.6 0.4 0.3 0.2 0.1
Univ. BC Neural Network 0.6 0.7 0.8 0.9 1 0.9 0.9 0.9 0.8
FSU Regression 0.3 0.4 0.4 0.4 0.4 0.4 0.5 0.6 0.6
TCD – UCLA 0.3 0.3 0.3 0.2 0.1 0 -0.1 -0.2 -0.2
UNB/CWC Nonlinear PCA 0.2 0.1 0 0 -0.1 0 0 0 0.1
Average, statistical models 0.5 0.5 0.6 0.6 0.5 0.4 0.4 0.3 0.3
Average, all models 0.5 0.6 0.7 0.7 0.7 0.7 0.6 0.6 0.5

Discussion of Current Forecasts

Most of the set of dynamical and statistical model predictions issued during late August and early September 2014 predict an onset of weak El Nino conditions during northern early fall 2014 with some further warming predicted into late fall and winter 2014-15. Development of El Nino conditions appears approximately 55 go 60% likely for the Sep-Nov season, rising to 70-75% by Nov-Jan through Jan-Mar 2014-15. In the most recent week, the SST anomaly in the Nino3.4 region was 0.5 C, reflecting borderline El Niño conditions. The monthly anomalous SSTs in the Niño3.4 region were near 0.5 during May and June, but returned to neutral levels during July and August. Based on the multi-model mean predictions, and the expected skill of the models by start time and lead time, the probabilities (X100) for La Niña, neutral and El Niño conditions (using -0.5C and 0.5C thresholds) over the coming 9 seasons are:

IRI/CPC Mid-Month Plume-Based ENSO Forecast Probabilities

Season La Niña Neutral El Niño
SON 2014 ~0% 44% 56%
OND 2014 ~0% 33% 67%
NDJ 2014 ~0% 28% 72%
DJF 2014 ~0% 28% 72%
JFM 2015 ~0% 28% 72%
FMA 2015 ~0% 35% 65%
MAM 2015 1% 40% 59%
AMJ 2015 4% 43% 53%
MJJ 2015 7% 44% 49%

Summary of forecasts issued over last 22 months

The following interactive plot shows the model forecasts issued not only from the current month (as in the plot above), but also from the 21 months previous to this month. The observations are shown up to the most recently completed 3-month period. The plots allow comparison of plumes from the previous start times, or examination of the forecast behavior of a given model over time.
Hovering over any single model will highlight that particular model in the chart.
Clicking a particular model will hide/show that model in the chart.
At the bottom of the plot, you can select which models to show in the chart: all the models, the dynamical models only, or the statistical models only.

Notes on the data 

Only models producing forecasts on a monthly basis are included. This means that some models whose forecasts appear in the Experimental Long-Lead Forecast Bulletin (produced by COLA) do not appear in the table.

Once an IRI ENSO probability forecast has been published, the results stand even if a model reports an error and changes their data. When this happens we will update the plume with the model's correct values even though our forecast hasn't changed. What this means is that our forecast is always the same, but the underlying data may be different from what we based our forecast on.

The SST anomaly forecasts are for the 3-month periods shown, and are for the Nino 3.4 region (120-170W, 5N-5S). Often, the anomalies are provided directly in a graph or a table by the respective forecasting centers for the Nino 3.4 region. In some cases, however, they are given for 1-month periods, for 3-month periods that skip some of the periods in the above table, and/or only for a region (or regions) other than Nino 3.4. In these cases, the following means are used to obtain the needed anomalies for the table:

  • Temporal averaging
  • Linear temporal interpolation
  • Visual averaging of values on a contoured map

The anomalies shown are those with respect to the base period used to define the normals, which vary among the groups producing model forecasts. They have not been adjusted to anomalies with respect to a common base period. Discrepancies among the climatological SST resulting from differing base periods may be as high as a quarter of a degree C in the worst cases. Forecasters are encouraged to use the standard 1991-2020 period as the base period, or a period not very different from it.

Historical SST Anomalies Image

References

Real-time ENSO forecast skill evaluated over the last two decades, with focus on the onset of ENSO events. Ehsan, M.A., L’Heureux, M.L., Tippett, M.K., Robertson, A.W, Turmelle, J.P., npj Clim Atmos Sci, 2024.

The IRI ENSO forecast is released on the 19th of each month. If the 19th falls on a weekend or holiday, it is released on the closest business day.

Forecast and model data used in our probabilistic forecast can be accessed by submitting a Request to Access IRI ENSO Data.

All data from this website is covered under the Creative Commons Attribution 4.0 License. When citing IRI ENSO images or data, please use "Images [or Data] provided by The International Research Institute for Climate and Society, Columbia University Climate School", with a link to https://iri.columbia.edu/ENSO.