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ENSO Forecasts

2013 September Quick Look

Published: September 24, 2013

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)

Use the navigation menu to navigate to the different forecast sections

During August through early September the observed ENSO conditions remained neutral. Most of the ENSO prediction models indicate a continuation of neutral ENSO through 2013 and the rst quarter of 2014. However, a few (mainly statistical) models call for cooling toward borderline or weak La Ni˜na
conditions for northern autumn into winter, while a few others (mainly dynamical) forecast a warming
toward borderline or weak El Ni˜no conditions for this same time frame.

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 Dec-Feb
  • Typically persist for 9-12 months, though occasionally persisting for up to 2 years
  • Typically recur every 2 to 7 years

Figure 1 is based on a consensus of CPC and IRI forecasters, in association with the official CPC/IRI ENSO Diagnostic Discussion

Figure 3 is purely objective, based on regression, using equally weighted model predictions from the plume

CPC/IRI ENSO Update

Published: September 05, 2013

El Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued jointly by the Climate Prediction Center/NCEP/NWS and the International Research Institute for Climate and Society

ENSO Alert System Status: Not Active

Synopsis: ENSO-neutral is favored through the Northern Hemisphere winter 2013-14.

ENSO-neutral conditions persisted during August 2013, as reflected by near-average sea surface temperatures (SSTs) across much of the equatorial Pacific, with below-average SSTs in the eastern Pacific (Fig. 1). Consistent with this pattern, weekly Niño-4 and Niño-3.4 indices were between -0.5 and 0.2°C, while Niño-3 and Niño-1+2 indices were at or cooler than -0.5°C (Fig. 2). The oceanic heat content (average temperature in the upper 300m of the ocean) remained near to slightly above average during August (Fig. 3), due to the persistence of above-average sub-surface temperatures across much of the eastern half of the Pacific (Fig. 4). The low-level and upper-level winds were near average across the equatorial Pacific. Convection continued to be enhanced over Indonesia and suppressed in the central and eastern Pacific (Fig. 5). Collectively, these atmospheric and oceanic conditions reflect ENSO-neutral.

Most model forecasts continue to predict ENSO-neutral (Niño-3.4 index between -0.5°C and 0.5°C) into the Northern Hemisphere spring 2014 (Fig. 6). For the next several seasons, the average of the statistical model forecasts is near -0.5°C, while the average of the dynamical model forecasts is near or just above 0.0°C. Similar to last month, the forecast consensus favors ENSO-neutral (60% chance or greater) through December – February 2013-14 (see CPC/IRI consensus forecast).

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 for the evolution of El Niño/La Niña are updated monthly in the Forecast Forum section of CPC’s Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 10 October 2013. 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.

CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
ASO 2013 19% 79% 2%
SON 2013 22% 74% 4%
OND 2013 24% 70% 6%
NDJ 2014 26% 64% 10%
DJF 2014 25% 62% 13%
JFM 2014 26% 58% 16%
FMA 2014 25% 56% 19%
MAM 2014 25% 54% 21%
AMJ 2014 24% 55% 21%

IRI Technical ENSO Update

Published: September 24, 2013

Recent and Current Conditions

The SST anomaly in the Nino3.4 region has been in the neutral range lately, through mid-September 2013. For August 2013 the Nino3.4 SST anomaly was -0.28 C, indicative of neutral ENSO conditions, and for May-August it was -0.27 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 0.0 C, indicating neutral ENSO conditions in the tropical Pacific; this is slightly warmer than the -0.28 C level observed in August.

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 high likelihood of neutral ENSO conditions enduring through the northern autumn, and into winter of 2013-14, with probabilities of El Niño or La Niña each less than 30% through that time. 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 exactly at their average. The SST continues to be slightly above average in the far western part of the basin, but has been below average in the eastern quarter of the basin since May. Subsurface temperature anomalies across the central and eastern equatorial Pacific have become slightly above average since June. In the atmosphere, the basin-wide sea level pressure pattern (e.g. the SOI), and the low-level zonal winds have been approximately average across much of the basin. The upper level zonal winds are leaning toward enhanced easterlies in the eastern part of the tropical Pacific, but with some residual enhanced westerlies in the western part. Anomalous convection (as measured by OLR) has generally been negative in the central and eastern tropical Pacific, and positive in the far western part of the basin. Together, these features reflect ENSO-neutral conditions. A tendency toward the cool part of the neutral range has weakened over the last month, and now most of the ENSO-related fields indicate more “middle-of-the road” neutral conditions.

As of mid-September, only 8% of the set of dynamical and statistical models models predicts weak La Niña SST conditions for the Sep-Nov 2013 season, none predicts El Niño conditions, so that 92% 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 season, among models that do use subsurface temperature information, 63% predicts ENSO-neutral SSTs, 26% predicts El Niño conditions and 11% predicts La Niña conditions. For all model types, the probability for neutral ENSO conditions ranges from 62% (for Dec-Feb 2013-14 and Jan-Mar 2014) to 92% (for Sep-Nov 2013) through the end of the forecast period in northern early summer 2014. (Note 1). 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 at 8% for Sep-Nov 2013, remaining near 10% through the end of the forecast period in early northern summer 2014. Model probabilities for ENSO-neutral conditions are 91% for Sep-Nov 2013, and ranging between 69% and 81% thereafter, through Mar-May 2014. By early summer 2014 probabilities for neutral drop to 51% due to the slightly rising probability for El Niño. Probabilities for El Niño are 1% for Sep-Nov 2013, 2% for Oct-Dec, and remain no higher than 10% through Jan-Mar 2014 and then rise to 36% for the final forecast period of May-Jul 2014. Clearly, the models collectively favor neutral ENSO conditions through to early 2014; La Niña is slightly favored over El Niño through early northern winter 2013-14, but then the tables turn and El Niño is favored from Jan-Mar 2014 through early northern summer 2014. 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 24 or more models on the IRI/CPC plume describe, on average, maintenance of neutral ENSO conditions during the coming months, continuing through the northern winter of 2013-14. Some uncertainty exists, but it is not great because we are past the period typically most likely for new ENSO event evolution. The model forecast spread expresses that uncertainty, ranging between weak La Niña and weak El Niño conditions, even though the majority of the forecasts is in the neutral range. Statistical models tend to call for development of weak La Niña conditions during late 2013 more than dynamical models. From late northern winter 2013-14 onward, more dynamical than statistical models begin forecasting weak El Niño conditions. 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.

IRI/CPC Plume-Based Probabilistic ENSO Forecast

Published: September 24, 2013



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

Season La Niña Neutral El Niño
SON 2013 8% 91% 1%
OND 2013 9% 89% 2%
NDJ 2014 10% 87% 3%
DJF 2014 9% 84% 7%
JFM 2014 9% 81% 10%
FMA 2014 9% 75% 16%
MAM 2014 9% 69% 22%
AMJ 2014 12% 58% 30%
MJJ 2014 13% 51% 36%

CPC/IRI Consensus Probabilistic ENSO Forecast

Published: September 05, 2013



CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
ASO 2013 19% 79% 2%
SON 2013 22% 74% 4%
OND 2013 24% 70% 6%
NDJ 2014 26% 64% 10%
DJF 2014 25% 62% 13%
JFM 2014 26% 58% 16%
FMA 2014 25% 56% 19%
MAM 2014 25% 54% 21%
AMJ 2014 24% 55% 21%

IRI/CPC ENSO Predictions Plume

Published: September 24, 2013

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.


Seasons (2013-2014)
Model SON OND NDJ DJF JFM FMA MAM AMJ MJJ
Dynamical models
NCEP CFS version 2 0.2 0.3 0.3 0.3 0.3 0.3 0.4 0.4
NASA GMAO model 0.3 0.4 0.4 0.5 0.5 0.5 0.5
Japan Met. Agency model 0 0 0.1 0.2 0.3
Scripps Inst. HCM 0.4 0.5 0.5 0.6 0.7 0.7 0.8 0.8 0.7
Lamont-Doherty model -0.5 -0.8 -1 -0.9 -0.7 -0.5 -0.3 0 0.4
POAMA (Austr) model -0.1 -0.2 -0.2 -0.1 0 0.1 0.2
ECMWF model 0.3 0.4 0.5 0.6 0.6
UKMO model -0.3 -0.5 -0.6
KMA (Korea) SNU model -0.1 0 0.1 0.3 0.3 0.4 0.4 0.4 0.4
ESSIC Intermed. Coupled model -0.2 -0.3 -0.3 -0.3 -0.3 -0.2 -0.1 0 0.1
COLA ANOM 0.2 0.6 0.8 0.7 0.5 0.3 0.1 0 -0.1
MÉT&#201O FRANCE model 0.1 0.1 0.2 0.2 0.3
Japan Frontier Coupled model -0.3 -0.3 -0.2 -0.1 -0.1 0 0 0.1 0.2
COLA CCSM3 model 0.4 0.5 0.6 0.6 0.7 0.8 0.8 0.7 0.6
CSIR-IRI 3-model MME -0.2 -0.2 -0.3 -0.5 -0.6
GFDL CM2.1 Coupled Climate model 0.1 0.2 0.2 0.3 0.4 0.6 0.6 0.7 1
Canadian Coupled Fcst Sys 0.1 0.1 0.1 0.2 0.2 0.3 0.3 0.3 0.3
Average, dynamical models 0 0 0.1 0.1 0.2 0.3 0.3 0.3 0.4
Statistical models
NCEP/CPC Markov model -0.6 -0.6 -0.4 -0.3 -0.2 -0.1 0 0 0.1
NOAA/CDC Linear Inverse -0.5 -0.5 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1
NCEP/CPC Constructed Analog -0.4 -0.3 -0.3 -0.3 -0.3 -0.2 -0.1 0.2 0.4
NCEP/CPC Can Cor Anal -0.5 -0.5 -0.5 -0.6 -0.5 -0.4 -0.3 -0.1 -0.1
Landsea/Knaff CLIPER -0.3 -0.4 -0.5 -0.6 -0.4 -0.2 -0.1 -0.1 -0.1
Univ. BC Neural Network -0.4 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3
FSU Regression -0.3 -0.3 -0.2 -0.2 -0.1 0 0.1 0.3 0.4
TDC – UCLA -0.4 -0.5 -0.6 -0.6 -0.6 -0.6 -0.5 -0.4 -0.4
Average, statistical models -0.4 -0.4 -0.4 -0.4 -0.3 -0.2 -0.1 0 0.1
Average, all models -0.1 -0.1 -0.1 0 0 0.1 0.1 0.2 0.3

Discussion of Current Forecasts

Most of the set of dynamical and statistical model predictions issued during late August and early September 2013 predict neutral ENSO conditions, although a few (mainly statistical) models indicate borderline or weak La Nina conditions for northern autumn and later, and a few dynamical models call for borderline El Nino conditions developing during the same period. In the most recent week, the SST anomaly in the Nino3.4 region was 0.0C. The average forecast of all models hints at a gradual warming tendency over the coming seasons. 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 Nina, neutral and El Nino 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 2013 8% 91% 1%
OND 2013 9% 89% 2%
NDJ 2014 10% 87% 3%
DJF 2014 9% 84% 7%
JFM 2014 9% 81% 10%
FMA 2014 9% 75% 16%
MAM 2014 9% 69% 22%
AMJ 2014 12% 58% 30%
MJJ 2014 13% 51% 36%

Summary of forecasts issued over last 22 months

The following plots show 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 also 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. The first plot shows forecasts for dynamical models, the second for statistical models, and the third for all models. For less difficult readability, forecasts are shown to a maximum of only the first five lead times. Below the third plot, we provide a mechanism for highlighting the forecasts of one model at a time against a background of more lightly colored lines for all other models.


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.

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 1971-2000 period as the base period, or a period not very different from it.