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ENSO Forecasts

2013 August Quick Look

Published: August 15, 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 July through early August the observed ENSO conditions remained neutral. Most of the ENSO prediction models indicate a continuation of neutral ENSO through the remainder of 2013 and into early 2014. However, a few (mainly statistical) models call for cooling toward borderline or weak La Niña conditions for northern autumn into winter, while a few others (mainly dynamical) forecast some warming toward borderline or weak El Ni˜ño 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: August 8, 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 into the Northern Hemisphere fall 2013.

ENSO-neutral conditions persisted during July 2013, as reflected by near-average sea surface temperatures (SSTs) across the central and east-central equatorial Pacific and below-average SSTs in the eastern Pacific (Fig. 1). Consistent with this pattern, weekly Niño-4 and Niño-3.4 values were between -0.5° and 0°C, while Niño-3 and Niño-1+2 indices remained cooler than -0.5°C (Fig. 2). The oceanic heat content (average temperature in the upper 300m of the ocean) anomalies continued to be slightly above average during July (Fig. 3), due to the persistence of above-average sub-surface temperatures in most of the eastern half of the Pacific (Fig. 4). The low-level winds remained near average across the equatorial Pacific, while weak upper-level westerly anomalies persisted in the western Pacific. Convection continued to be enhanced over Indonesia and suppressed in the central part of the basin (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). The statistical model forecasts remain cooler in the Niño-3.4 region relative to the dynamical model forecasts. Similar to last month, the forecast consensus favors ENSO-neutral (60% chance or greater) through October – December 2013 (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 Niño are updated monthly in the Forecast Forum section of CPC’s Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 5 Sep 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
JAS 2013 15% 82% 3%
ASO 2013 19% 73% 8%
SON 2013 21% 66% 13%
OND 2013 23% 60% 17%
NDJ 2014 25% 56% 19%
DJF 2014 26% 55% 19%
JFM 2014 26% 55% 19%
FMA 2014 25% 57% 18%
MAM 2014 24% 58% 18%

IRI Technical ENSO Update

Published: August 15, 2013

Recent and Current Conditions

The SST anomaly in the Nino3.4 region has been in the neutral range lately, through mid-August 2013. For July 2013 the Nino3.4 SST anomaly was -0.31 C, indicative of neutral ENSO conditions, and for April-June it was -0.26 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 -0.3 C, indicating neutral ENSO conditions in the tropical Pacific; this is about the same as the -0.31 C level observed in July.

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 rest of the northern summer, the 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-August, now available in the IRI/CPC ENSO prediction plume, is discussed below. Currently, Nino3.4 SST anomalies are just slightly negative. The SST continues to be slightly above average in the far western part of the basin, but have been below average in the eastern quarter of the basin since May. Subsurface temperature anomalies across the equatorial Pacific have been mixed, but overall have averaged near to slightly above average since June. In the atmosphere, the basin-wide sea level pressure pattern (e.g. the SOI), has been somewhat above average (indicative of somewhat cool ENSO conditions) but the low-level zonal winds have not been far from average across much of the basin. The upper level zonal winds lean toward enhanced westerlies, indicative of cool ENSO conditions. 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, with a tendency toward the cool part of average. However, all fields taken collectively do not indicate weak La Niña conditions, but rather cool-neutral conditions.

As of mid-august, 17% of the set of dynamical and statistical models models predicts weak La Niña SST conditions for the Aug-Oct 2013 season, 4% predicts El Niño conditions, and 78% 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 Nov-Jan season, among models that do use subsurface temperature information, 76% predicts ENSO-neutral SSTs, 6% predicts El Niño conditions and 18% predicts La Niña conditions. For all model types, the probability for neutral ENSO conditions ranges from 65% (for Oct-Dec 2013) to 81% (for Dec-Feb 2013-14 and Mar-May 2014) through the end of the forecast period in northern spring 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 19% for Aug-Oct 2013, remaining near 20% through Nov-Jan and then between 10% and 17% from Dec-Feb 2013-14 to Apr-Jun 2014. Model probabilities for ENSO-neutral conditions are 80% for Aug-Oct 2013, and ranging between 72% and 76% through early 2014. Meanwhile, probabilities for El Niño are 1% for Aug-Oct 2013, 3% for Sep-Nov, and remain no higher than 10% through Jan-Mar 2014 and then rise to 32% for the final forecast period of Apr-Jun 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. 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. More statistical models call for development of weak La Niña than the small set of dynamical models calling for development of weak El Niño. 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 August by CPC and IRI, which will include some human judgement in combination with the model guidance.

Using the 0.5 C thresholds, the climatological probabilities of La Nina, neutral, and El Nino conditions for each 3-month season are as follows:

 

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%

Note 1 – Only models that produce a new ENSO prediction every month are included in the above statement.

IRI/CPC Plume-Based Probabilistic ENSO Forecast

Published: August 15, 2013



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

Season La Niña Neutral El Niño
ASO 2013 19% 80% 1%
SON 2013 23% 74% 3%
OND 2013 23% 73% 4%
NDJ 2014 18% 76% 6%
DJF 2014 17% 76% 7%
JFM 2014 14% 76% 10%
FMA 2014 11% 72% 17%
MAM 2014 11% 66% 23%
AMJ 2014 11% 57% 32%

CPC/IRI Consensus Probabilistic ENSO Forecast

Published: August 8, 2013



CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
JAS 2013 15% 82% 3%
ASO 2013 19% 73% 8%
SON 2013 21% 66% 13%
OND 2013 23% 60% 17%
NDJ 2014 25% 56% 19%
DJF 2014 26% 55% 19%
JFM 2014 26% 55% 19%
FMA 2014 25% 57% 18%
MAM 2014 24% 58% 18%

IRI/CPC ENSO Predictions Plume

Published: August 15, 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.


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

Seasons (2013-2014)
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 ANOM0.2 0.6 0.8 0.7 0.5 0.3 0.1 0 -0.1
MÉTÉO 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
ASO 2013 19% 80% 1%
SON 2013 23% 74% 3%
OND 2013 23% 73% 4%
NDJ 2014 18% 76% 6%
DJF 2014 17% 76% 7%
JFM 2014 14% 76% 10%
FMA 2014 11% 72% 17%
MAM 2014 11% 66% 23%
AMJ 2014 11% 57% 32%

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.