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IRI ENSO Forecast

2014 November Quick Look

Published: November 20, 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)

Use the navigation menu on the right to navigate to the different forecast sections

During late October through early November the SST exceeded thresholds for weak Niño conditions, although only some of the atmospheric variables indicate an El Niño pattern. Most of the ENSO prediction models indicate weak El Niño conditions during the November-January season in progress, continuing well into the northern spring 2015.

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: November 6, 2014

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: El Niño Watch

Synopsis: There is a 58% chance of El Niño during the Northern Hemisphere winter, which is favored to last into the Northern Hemisphere spring 2015.

During October 2014, above-average sea surface temperatures (SST) increased slightly across the eastern half of the equatorial Pacific (Fig. 1). The weekly Niño indices were between +0.6°C (Niño-3.4 and Niño-1+2) and +0.9°C (Niño-3) at the end of the month (Fig. 2). Subsurface heat content anomalies (averaged between 180º-100ºW) were largely unchanged (Fig. 3) even as a new downwelling Kelvin wave increased temperatures at depth in the central Pacific (Fig. 4). The monthly equatorial low-level winds were near average, although anomalous westerlies continued to emerge on occasion. Upper-level winds were also mostly average across the Pacific. The Southern Oscillation Index continued to be negative, accompanied by mostly average rainfall near the Date Line and suppressed rainfall over Indonesia (Fig. 5). Overall, several features across the tropical Pacific are characteristic of borderline El Niño conditions, but collectively, the combined atmosphere and oceanic state remains ENSO-neutral. Similar to last month, most models predict El Niño to develop during October-December 2014 and to continue into early 2015 (Fig. 6). However, the ongoing lack of clear atmosphere-ocean coupling and the latest NCEP CFSv2 model forecast (Fig. 7) have reduced confidence that El Niño will fully materialize (at least five overlapping consecutive 3-month values of the Niño-3.4 index at or greater than 0.5°C). If El Niño does emerge, the forecaster consensus favors a weak event. In summary, there is a 58% chance of El Niño during the Northern Hemisphere winter, which is favored to last into the Northern Hemisphere spring 2015 (click  (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 4 December 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.

CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
OND 2014 ~0% 47% 53%
NDJ 2014 ~0% 42% 58%
DJF 2014 1% 41% 58%
JFM 2015 1% 41% 58%
FMA 2015 2% 43% 55%
MAM 2015 2% 45% 53%
AMJ 2015 3% 47% 50%
MJJ 2015 6% 48% 46%
JJA 2015 8% 49% 43%


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: November 20, 2014

Recent and Current Conditions

The SST anomaly in the NINO3.4 region has hovered near or just below the threshold of the level required for El Niño level, beginning in early November the weekly SST anomalies have started exceeded it. For October the average NINO3.4 SST anomaly was 0.49 C, indicative of borderline Niño conditions, and for Aug-Oct it was 0.38 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 0.8 C, in the category of weak El Niño for SST.  However, accompanying this SST is an atmospheric pattern with inadequate indication of an El Niño-like pattern–very weak westerly low-level wind anomalies and no positive anomalies of convection near the dateline. Some indicators, however, such as the Southern Oscillation Index (SOI), have recently assumed values indicative of weak El Niño, and the upper level wind anomalies are also showing El Niño-indicative enhanced easterlies.

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 58% likelihood for a transition from neutral ENSO conditions to El Niño conditions during the remainder of fall 2014 now in progress, and into winter.  The latest set of model ENSO predictions, from mid-November, now available in the IRI/CPC ENSO prediction plume, is discussed below. Currently, Nino3.4 SST anomalies are about 0.8C, above the 0.5C threshold for weak El Niño. Subsurface temperature anomalies across the eastern equatorial Pacific have remained somewhat above average, and in fact increased slightly during the last few weeks. In the atmosphere, the basin-wide sea level pressure pattern (e.g. the SOI) has recently exceeded the threshold of -10 for a weak El Niño. However, other atmospheric parameters continue to reflect neutral or warm-neutral ENSO conditions: Weak anomalous low-level westerlies have appeared at times during October and early November but have not been sustained or particularly strong. Upper level anomalous westerlies are also being observed over parts of the central equatorial Pacific. Anomalous convection (as measured by OLR) has been near average, or even below average, near and eastward of the dateline, and over much of Indonesia, and enhanced in a portions of the far western tropical Pacific.  Together, the oceanic and atmospheric features currently reflect a warmish but neutral ENSO condition, despite the weak El Niño status of the SST during the last few weeks.

As of mid-November, none of the dynamical or statistical models models predicts La Niña SST conditions for the initial Nov-Jan 2014-15 season, 88% predicts El Niño conditions, and 12% 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 Feb-Apr 2015 season, among models that do use subsurface temperature information, 19% predicts ENSO-neutral SSTs, 81% predicts El Niño conditions and none predicts La Niña conditions. For all model types, the probability for neutral ENSO conditions is 20% or below between Nov-Jan 2014-15 through Jan-Mar, and 30% or below through Jun-Aug 2015. Probabilities for El Niño rise are 80-88% between Nov-Jan 2014-15 through Jan-Mar, and at least 70% out to May-July 2015. No model predicts La Niña conditions for any of the 3-month periods between Nov-Jan 2014-15 and Jul-Sep 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 Nov-Jan 2014-15 through Apr-Jun 2015, rising to 3% by May-Jul and 11% by Jul-Sep.  Model probabilities for neutral ENSO conditions are 25% for the initial period of Nov-Jan 2014-15, 26% for the next running period of Dec-Feb, and rise to 32% by Feb-Apr 2015, and to 43 by Jul-Sep. Probabilities for El Niño are 75% for Nov-Jan 2014-15, 74% for Dec-Feb, 72% for Jan-Mar 2015, and slowly decline to 46% for Jul-Sep 2015. The models collectively favor El Niño over other ENSO conditions by a sizable margin until Apr-Jun 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, El Niño conditions for the Nov-Jan 2014-15 season currently in progress, enduring well into northern spring season of 2015. 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 very unlikely. 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

IRI/CPC Plume-Based Probabilistic ENSO Forecast

Published: November 20, 2014



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

Season La Niña Neutral El Niño
NDJ 2014 ~0% 25% 75%
DJF 2014 ~0% 26% 74%
JFM 2015 ~0% 28% 72%
FMA 2015 ~0% 32% 68%
MAM 2015 ~0% 34% 66%
AMJ 2015 ~0% 39% 61%
MJJ 2015 3% 40% 57%
JJA 2015 7% 40% 53%
JAS 2015 11% 43% 46%

IRI ENSO Forecast

CPC/IRI Consensus Probabilistic ENSO Forecast

Published: November 6, 2014



CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
OND 2014 ~0% 47% 53%
NDJ 2014 ~0% 42% 58%
DJF 2014 1% 41% 58%
JFM 2015 1% 41% 58%
FMA 2015 2% 43% 55%
MAM 2015 2% 45% 53%
AMJ 2015 3% 47% 50%
MJJ 2015 6% 48% 46%
JJA 2015 8% 49% 43%

IRI ENSO Forecast

IRI/CPC ENSO Predictions Plume

Published: November 20, 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.


Seasons (2014-2015)
Model NDJ DJF JFM FMA MAM AMJ MJJ JJA JAS
Dynamical models
NCEP CFS version 2 0.8 0.6 0.6 0.7 0.8 1 1.3 1.7
NASA GMAO model 1 1.2 1.3 1.4 1.3 1.2 1.2
Japan Met. Agency model 0.7 0.7 0.7 0.7 0.7
Scripps Inst. HCM 0.9 0.9 0.9 0.8 0.7 0.6 0.6 0.5 0.6
Lamont-Doherty model 0.3 0.3 0.3 0.4 0.6 1 1.3 1.4 1.3
POAMA (Austr) model 0.6 0.6 0.7 0.7 0.7 0.7 0.7
ECMWF model 0.8 0.8 0.8 0.7 0.8
UKMO model 0.6 0.4 0.3 0.3
KMA (Korea) SNU model 0.6 0.7 0.8 0.7 0.7 0.7 0.6 0.6 0.5
ESSIC Intermed. Coupled model 0.8 0.8 0.7 0.5 0.4 0.3 0.1 0 -0.1
COLA CCSM3 model 0.6 0.8 0.8 0.6 0.5 0.5 0.6 0.4 0
MÉTÉO FRANCE model 0.7 0.7 0.7 0.7 0.6
Japan Frontier Coupled model 0.9 1 1.1 1 1 0.9 0.9 0.8 0.6
CSIR-IRI 3-model MME 0.9 1.1 1.1 0.9 0.7 0.6
GFDL CM2.1 Coupled Climate model 1.1 1.3 1.4 1.3 1.2 1.1 1 0.8 0.7
Canadian Coupled Fcst Sys 1 1.1 1 1 0.9 0.8 0.7 0.6 0.6
GFDL CM2.5 FLOR Coupled Climate model 0.8 0.9 1 1.1 1 1 0.9 0.7 0.6
Average, dynamical models 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.7 0.5
Statistical models
NCEP/CPC Markov model 0.6 0.7 0.7 0.6 0.6 0.6 0.6 0.5 0.6
NOAA/CDC Linear Inverse 0.4 0.3 0.3 0.2 0.2 0.1 0.1 0.1 0.1
NCEP/CPC Constructed Analog 0.9 0.9 0.8 0.6 0.6 0.4 0.3 0.2 0.1
NCEP/CPC Can Cor Anal 1.1 0.9 0.7 0.6 0.6 0.6 0.5 0.5 0.5
Landsea/Knaff CLIPER 0.5 0.4 0.4 0.3 0.3 0.3 0.3 0.1 0
Univ. BC Neural Network 0.5 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6
FSU Regression 0.6 0.6 0.5 0.5 0.5 0.5 0.5 0.5 0.5
TCD – UCLA 0.6 0.7 0.6 0.6 0.4 0.3 0.3 0.3 0.3
UNB/CWC Nonlinear PCA 0.4 0.4 0.3 0.3 0.2 0.2 0.2 0.2 0.3
Average, statistical models 0.6 0.6 0.5 0.5 0.4 0.4 0.4 0.3 0.3
Average, all models 0.7 0.7 0.7 0.7 0.7 0.6 0.6 0.6 0.4

Discussion of Current Forecasts

Most of the set of dynamical and statistical model predictions issued during late October and early November 2014 predict weak El Niño conditions from late northern fall 2014 through winter 2014-15 and much of spring 2015. Development of El Niño conditions appears approximately 70-75% likely for the Nov-Jan 2014-15 through Jan-Mar 2015 seasons, dropping to 60-70% for Feb-Apr through Apr-Jun 2015. In the most recent week, the SST anomaly in the Nino3.4 region was 0.8 C, reflecting weak El Niño conditions. Some atmospheric variables do not reflect El Niño, however. The monthly anomalous SSTs in the Niño3.4 region were 0.45 and 0.49 C for September and October, respectively. 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
NDJ 2014 ~0% 25% 75%
DJF 2014 ~0% 26% 74%
JFM 2015 ~0% 28% 72%
FMA 2015 ~0% 32% 68%
MAM 2015 ~0% 34% 66%
AMJ 2015 ~0% 39% 61%
MJJ 2015 3% 40% 57%
JJA 2015 7% 40% 53%
JAS 2015 11% 43% 46%

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.