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IRI ENSO Forecast

2013 October Quick Look

Published: October 17, 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 on the right to navigate to the different forecast sections

During September through October the observed ENSO conditions remained neutral. Most of the ENSO prediction models indicate a continuation of neutral ENSO through 2013 and the first quarter of 2014. A long-lasting mean disagreement between statistical and dynamical models (statistical leaning cooler, dynamical warmer) has diminished. The average forecast of all models indicates a gradual warming tendency during the first half of 2014.

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

IRI ENSO Forecast

CPC/IRI ENSO Update

Published: October 10, 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 expected into the Northern Hemisphere spring 2014.

ENSO-neutral continued during September 2013, as sea surface temperature (SST) anomalies were near-average across much of the equatorial Pacific Ocean(Fig. 1). Except for the Niño-1+2 region, all of the latest weekly Niño index values were between 0°C and -0.5°C  (Fig. 2).  The oceanic heat content (average temperature in the upper 300m of the ocean) weakened  (Fig. 3), as a consequence of an upwelling oceanic Kelvin wave contributing to below-average temperatures in the east-central Pacific Ocean  (Fig. 4).The strength of the tropical atmospheric circulation anomalies, as reflected by convection and winds, also weakened over the last month.  Slightly enhanced convection remained over parts of Indonesia, with weakly suppressed convection evident near the Date Line  (Fig. 5).  Low-level winds were near average, while anomalous westerly winds prevailed at upper-levels.  Collectively, these atmospheric and oceanic conditions reflect ENSO-neutral.

The majority of model forecasts indicate that ENSO-neutral (Niño-3.4 index between -0.5°C and 0.5°C) will persist into the Northern Hemisphere spring 2014 (Fig. 6). Though the forecast favors near-average conditions, many models predict a gradual increase from slightly cooler than average to warmer conditions as the spring approaches.  Overall, the consensus forecast is for ENSO-neutral to continue into the Northern Hemisphere spring 2014 (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
SON 2013 8% 88% 4%
OND 2013 10% 81% 9%
NDJ 2014 10% 76% 14%
DJF 2014 10% 72% 18%
JFM 2014 11% 69% 21%
FMA 2014 11% 65% 24%
MAM 2014 11% 62% 27%
AMJ 2014 12% 62% 26%
MJJ 2014 12% 58% 30%


Figure 7. NCEP CFSv2 forecasts of sea surface temperature (SST) anomalies for the Niño 3.4 region (5°N-5°S, 120°W-170°W). Figure updated 3 November 2014.

IRI ENSO Forecast

IRI Technical ENSO Update

Published: October 17, 2013

Recent and Current Conditions

The SST anomaly in the Nino3.4 region has been in the neutral range lately, through mid-October 2013. For September 2013 the Nino3.4 SST anomaly was -0.03 C, indicative of neutral ENSO conditions, and for July-September it was -0.21 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 just slightly below average ENSO conditions in the tropical Pacific; this is slightly cooler than the -0.03 C level observed in September.

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 into winter 2013-14, and through spring 2014, 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 slightly negative but in the ENSO-neutral range. 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 were slightly above average from mid-May through September, but are now very close to average in October. 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 indicate enhanced westerlies in part of the eastern tropical Pacific. Anomalous convection (as measured by OLR) has generally been negative in the central 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 continues, after a relative weakening of even slightly cool conditions during September.

As of mid-October, only 11% of the set of dynamical and statistical models models predicts weak La Niña SST conditions for the Oct-Dec 2013 season, none predicts El Niño conditions, so that 89% 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 Jan-Mar 2014 season, among models that do use subsurface temperature information, 79% predicts ENSO-neutral SSTs, 7% predicts El Niño conditions and 14% predicts La Niña conditions. For all model types, the probability for neutral ENSO conditions is near 90% for Oct-Nov-Dec 2013 to Dec-Jan Feb 2013-14, between 80% and 90% from Jan-Feb-Mar through Apr-May-Jun 2014, and between 70% and 80% for May-Jun-Jul and Jun-Jul-Aug 2014 at the end of the forecast period (Note 1 Below). 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.

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

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 5% for Oct-Dec 2013, remaining between 5% and 11% through the end of the forecast period in northern summer 2014. Model probabilities for ENSO-neutral conditions are between 90% and 95% from Oct-Dec 2013 to Jan-Mar 2014, dropping steadily during northern spring 2014, to become near or just below 50% by northern summer. The probabilities for ENSO-neutral drop due to a rising (but never dominating) probability for El Niño. Probabilities for El Niño are 5% or less from Oct-Dec 2013 to Jan-Mar 2014, thereafter steadily increasing to exceed 30% by Apr-Jun 2014 and to 42% by the final forecast period of Jun-Aug. It is clear that the models collectively favor neutral ENSO conditions through northern spring 2014; then by Apr-Jun El Niño probabilities become more competitive with ENSO-neutral probabilities, until they are approximately equally likely by Jun-Aug 2014 (both just shy of 50% due to the lingering 9% likelihood of La Niña).

figure3

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, maintenance of neutral ENSO conditions during the coming months, continuing into the northern spring of 2014. A continuing mean disagreement between statistical and dynamical models has diminished somewhat for this latest set of model forecasts. 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.

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%

IRI ENSO Forecast

IRI/CPC Plume-Based Probabilistic ENSO Forecast

Published: October 17, 2013



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

Season La Niña Neutral El Niño
OND 2013 5% 95% ~0%
NDJ 2014 6% 93% 1%
DJF 2014 7% 91% 2%
JFM 2014 6% 90% 4%
FMA 2014 6% 82% 12%
MAM 2014 6% 73% 21%
AMJ 2014 9% 58% 33%
MJJ 2014 11% 49% 40%
JJA 2014 10% 48% 42%

IRI ENSO Forecast

CPC/IRI Consensus Probabilistic ENSO Forecast

Published: October 10, 2013



CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
SON 2013 8% 88% 4%
OND 2013 10% 81% 9%
NDJ 2014 10% 76% 14%
DJF 2014 10% 72% 18%
JFM 2014 11% 69% 21%
FMA 2014 11% 65% 24%
MAM 2014 11% 62% 27%
AMJ 2014 12% 62% 26%
MJJ 2014 12% 58% 30%

IRI ENSO Forecast

IRI/CPC ENSO Predictions Plume

Published: October 17, 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 OND NDJ DJF JFM FMA MAM AMJ MJJ JJA
Dynamical models
NCEP CFS version 2 0.2 0.3 0.4 0.4 0.5 0.5 0.6 0.5
Japan Met. Agency model -0.1 0 0.1 0.2 0.3
Scripps Inst. HCM 0.3 0.4 0.5 0.6 0.7 0.7 0.7 0.7 0.7
Lamont-Doherty model -0.7 -0.9 -1 -0.8 -0.6 -0.4 -0.1 0.3 0.6
POAMA (Austr) model -0.3 -0.2 -0.1 0.1 0.2 0.3 0.4
ECMWF model 0.1 0.2 0.3 0.3 0.3
UKMO model -0.3 -0.4 -0.4
KMA (Korea) SNU model -0.1 0.1 0.2 0.3 0.3 0.4 0.4 0.4 0.4
ESSIC Intermed. Coupled model -0.3 -0.3 -0.3 -0.3 -0.2 -0.1 -0.1 0 0.1
MÉTÉO FRANCE model 0.3 0.4 0.4 0.4 0.4
CSIR-IRI 3-model MME -0.3 -0.4 -0.5 -0.5 -0.4
Canadian Coupled Fcst Sys 0 0.1 0.2 0.2 0.3 0.3 0.4 0.6 0.7
Average, dynamical models -0.1 -0.1 0 0.1 0.2 0.2 0.3 0.4
Statistical models
NCEP/CPC Markov model -0.7 -0.5 -0.4 -0.3 -0.2 -0.1 -0.1 0 0
NCEP/CPC Constructed Analog -0.3 -0.2 -0.3 -0.3 -0.3 -0.1 0.1 0.3 0.4
NCEP/CPC Can Cor Anal -0.4 -0.4 -0.4 -0.3 -0.2 0 0.1 0.2 0.2
Landsea/Knaff CLIPER -0.1 -0.1 -0.1 -0.1 0.1 0.3 0.5 0.4 0.4
Univ. BC Neural Network -0.3 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3
FSU Regression 0.1 0.1 0.1 0.1 0.2 0.3 0.4 0.4 0.5
TDC – UCLA -0.1 -0.1 -0.1 -0.1 0 0.1 0.2 0.2 0.3
Average, statistical models -0.2 -0.2 -0.2 -0.2 -0.1 0.1 0.2 0.3 0.3
Average, all models -0.2 -0.1 -0.1 0 0.1 0.1 0.3 0.3 0.4

Discussion of Current Forecasts

Most of the set of dynamical and statistical model predictions issued during late September and early October 2013 predict neutral ENSO conditions through the rest of 2013 and into early 2014, with a warming tendency during northern spring and summer 2014. Development of weak El Nino conditions appears possible by the middle of 2014. In the most recent week, the SST anomaly in the Nino3.4 region was -0.3C. 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
OND 2013 5% 95% ~0%
NDJ 2014 6% 93% 1%
DJF 2014 7% 91% 2%
JFM 2014 6% 90% 4%
FMA 2014 6% 82% 12%
MAM 2014 6% 73% 21%
AMJ 2014 9% 58% 33%
MJJ 2014 11% 49% 40%
JJA 2014 10% 48% 42%

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.