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2014 December Quick Look

Published: December 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 November through early December 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 December-February season in progress, continuing through most or all of northern spring 2015.

Figures 1 and 3 (the official CPC ENSO probability forecast and the objective model-based IRI ENSO probability forecast, respectively) are often quite similar. However, occasionally they may differ noticeably. There can be several reasons for differences. One possible reason is that the human forecasters, using their experience and judgment, may disagree to some degree with the models, which may have known biases. Another reason is related to the fact that 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, so that between the second and the third Thursday of the month, the official forecast (Fig. 1) has just been updated, while the model-based forecasts (Figs. 3 and 4) are still from the third Thursday of the previous month. On the other hand, from the third Thursday of the month until the second Thursday of the next month, the model-based forecasts are more recently updated, while the official forecasts remain from the second Thursday of the current month.
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: December 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: There is an approximately 65% chance that El Niño conditions will be present during the Northern Hemisphere winter and last into the Northern Hemisphere spring 2015.

During November 2014, sea surface temperature (SST) anomalies increased across the central and eastern equatorial Pacific (Fig. 1). At the end of the month, the weekly Niño indices ranged from +0.4°C in the Niño-1+2 region to +1.0°C in the Niño-3.4 region (Fig. 2). The subsurface heat content anomalies (averaged between 180º-100ºW) also increased during November (Fig. 3) as a downwelling oceanic Kelvin wave increased subsurface temperatures in the central and eastern Pacific (Fig. 4). However, the overall atmospheric circulation has yet to show a clear coupling to the anomalously warm waters. The monthly equatorial low-level winds were largely near average, although weak anomalous westerlies appeared in a portion of the eastern tropical Pacific. Upper level easterly anomalies emerged in the central and eastern tropical Pacific during the month. The Southern Oscillation Index has been somewhat negative, but the equatorial Southern Oscillation Index has been near zero. Also, rainfall continued to be below average near the Date Line and over Indonesia, and near average east of the Date Line (Fig. 5). Although the SST anomalies alone might imply weak El Niño conditions, the patterns of wind and rainfall anomalies generally do not clearly indicate a coupling of the atmosphere to the ocean. Therefore, despite movement toward El Niño from one month ago, the combined atmospheric and oceanic state remains ENSO-neutral.

Similar to last month, most models predict SST anomalies to be at weak El Niño levels during November-January 2014-15 and to continue above the El Niño threshold into early 2015 (Fig. 6). Assuming that El Niño fully emerges, the forecaster consensus favors a weak event. In summary, there is an approximately 65% chance of El Niño conditions during the Northern Hemisphere winter, which are expected to last into the Northern Hemisphere spring 2015 (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 8 January 2015. 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
NDJ 2014 ~0% 34% 66%
DJF 2014 ~0% 36% 64%
JFM 2015 1% 39% 60%
FMA 2015 1% 41% 58%
MAM 2015 2% 44% 54%
AMJ 2015 3% 45% 52%
MJJ 2015 5% 49% 46%
JJA 2015 7% 49% 44%
JAS 2015 9% 49% 42%

IRI ENSO Forecast

IRI Technical ENSO Update

Published: December 18, 2014

Recent and Current Conditions

The SST anomaly in the NINO3.4 region has been at the weak El Niño level from mid-October to the present, and even reached the borderline of moderate El Niño for a single week at the end of November.  For November the average NINO3.4 SST anomaly was 0.85 C, indicative of weak Niño conditions, and for Aug-Oct it was 0.60 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 0.9 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 been somewhat 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 66% likelihood for El Niño conditions during the Nov-Jan season now in progress, remaining at 60% or more through Jan-Mar 2015.  The latest set of model ENSO predictions, from mid-December, now available in the IRI/CPC ENSO prediction plume, is discussed below. Currently, Nino3.4 SST anomalies are about 0.9C, above the 0.5C threshold for weak El Niño. Subsurface temperature anomalies across the eastern equatorial Pacific have remained above average. In the atmosphere, the basin-wide sea level pressure pattern (e.g. the SOI) has been near the threshold of -0.8 to -0.10 for a weak El Niño in late November and early December, but recently weakened back toward neutral levels. Also, other atmospheric parameters continue to reflect neutral ENSO conditions: Weak anomalous low-level westerlies have only appeared at times during November and early December. Upper level anomalous easterly anomalies are being observed over substantial portions of the equatorial Pacific, indicative of El Niño. On the other hand, anomalous convection (as measured by OLR) has been near average, or even below average, near and eastward of the dateline.  Together, the oceanic and atmospheric features currently reflect a warmish but neutral ENSO condition, despite the clearly weak El Niño status of the SST during the last one to two months.

As of mid-December, none of the dynamical or statistical models models predicts La Niña SST conditions for the initial Dec-Feb 2014-15 season, 96% predicts El Niño conditions, and 4% 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 Mar-May 2015 season, among models that do use subsurface temperature information, 20% predicts ENSO-neutral SSTs, 80% predicts El Niño conditions and none predicts La Niña conditions. For all model types, the probability for neutral ENSO conditions is 32% or below between Dec-Feb 2014-15 through Apr-Jun 2015, and 50% or below through Jul-Sep. Probabilities for El Niño are 84% or higher between Dec-Feb 2014-15 and Jan-Mar, and at least 70% out to Apr-Jun 2015. No model predicts La Niña conditions for any of the 3-month periods between Dec-Feb 2014-15 and Aug-Oct 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 Dec-Feb 2014-15 through Apr-Jun 2015, rising to 5% by Jun-Aug and 14% by Aug-Oct.  Model probabilities for neutral ENSO conditions are 17% for the initial period of Dec-Feb 2014-15, 24% for the next running period of Jan-Mar 2015, and rise to 39% by Apr-Jun, and to 40-45% for May-Jul through Aug-Oct. Probabilities for El Niño are 83% for Dec-Feb 2014-15, 76% for Jan-Mar 2015, 70% for Feb-Apr, and do not fall below 50% until Aug-Oct when they are 46%. 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 Dec-Feb 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 cannot be ruled out. A strong event appears virtually impossible. 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
DJF 2014 ~0% 17% 83%
JFM 2015 ~0% 24% 76%
FMA 2015 ~0% 30% 70%
MAM 2015 ~0% 35% 65%
AMJ 2015 ~0% 39% 61%
MJJ 2015 2% 42% 56%
JJA 2015 5% 41% 54%
JAS 2015 8% 41% 51%
ASO 2015 14% 40% 46%

ENSO Forecast

IRI Model-Based Probabilistic ENSO Forecast

Published: December 18, 2014

A purely objective ENSO probability forecast, based on regression, using as input the model predictions from the plume of dynamical and statistical forecasts shown in the ENSO Predictions Plume. Each of the forecasts is weighted equally. It is updated near or just after the middle of the month, using forecasts from the plume models that are run in the first half of the month. It does not use any human interpretation or judgment. This is updated on the third Thursday of the month.

IRI ENSO Forecast Histogram Image

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

Season La Niña Neutral El Niño
DJF 2014 ~0% 17% 83%
JFM 2015 ~0% 24% 76%
FMA 2015 ~0% 30% 70%
MAM 2015 ~0% 35% 65%
AMJ 2015 ~0% 39% 61%
MJJ 2015 2% 42% 56%
JJA 2015 5% 41% 54%
JAS 2015 8% 41% 51%
ASO 2015 14% 40% 46%

ENSO Forecast

CPC Official Probabilistic ENSO Forecast

Published: December 4, 2014

The official CPC ENSO probability forecast, based on a consensus of CPC and IRI forecasters. It is updated during the first half of the month, in association with the official CPC ENSO Diagnostic Discussion. It is based on observational and predictive information from early in the month and from the previous month. It uses human judgment in addition to model output, while the forecast shown in the Model-Based Probabilistic ENSO Forecast relies solely on model output. This is updated on the second Thursday of every month.

NOAA?CPC ENSO Forecast Image
NOAA/CPC ENSO Forecast Graphic, courtesy of NOAA/CPC

CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
NDJ 2014 ~0% 34% 66%
DJF 2014 ~0% 36% 64%
JFM 2015 1% 39% 60%
FMA 2015 1% 41% 58%
MAM 2015 2% 44% 54%
AMJ 2015 3% 45% 52%
MJJ 2015 5% 49% 46%
JJA 2015 7% 49% 44%
JAS 2015 9% 49% 42%

ENSO Forecast

IRI ENSO Predictions Plume

Published: December 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 DJF JFM FMA MAM AMJ MJJ JJA JAS ASO
Dynamical models
NCEP CFS version 2 0.5 0.4 0.4 0.5 0.7 1 1.3 1.7
NASA GMAO model 1 1 1 1 0.9 0.9 0.9
Japan Met. Agency model 0.9 0.9 0.8 0.7 0.7
Scripps Inst. HCM 0.9 0.9 0.8 0.7 0.6 0.6 0.5 0.6 0.6
Lamont-Doherty model 0.6 0.6 0.6 0.8 1 1.3 1.5 1.5 1.5
POAMA (Austr) model 0.6 0.5 0.5 0.5 0.5 0.6 0.6
ECMWF model 0.8 0.8 0.7 0.7 0.9
UKMO model 0.8 0.6 0.5 0.4
KMA (Korea) SNU model 0.8 0.8 0.8 0.8 0.8 0.7 0.7 0.6 0.6
COLA CCSM3 model 0.6 0.6 0.4 0.1 0 -0.1 -0.2 -0.2 -0.2
MÉTÉO FRANCE model 0.8 0.8 0.7 0.7 0.7
Japan Frontier Coupled model 1.1 1.1 1 0.9 0.8 0.7 0.6 0.4 0.2
CSIR-IRI 3-model MME 0.9 0.9 0.8 0.6 0.5 0.4
GFDL CM2.1 Coupled Climate model 1 1.1 1.2 1.2 1.3 1.3 1.2 0.9 0.6
Canadian Coupled Fcst Sys 0.9 0.7 0.7 0.7 0.7 0.7 0.8 0.7 0.5
GFDL CM2.5 FLOR Coupled Climate model 1 1.1 1.1 1.1 1 0.9 0.8 0.5 0.3
Average, dynamical models 0.8 0.8 0.8 0.7 0.7 0.8 0.8 0.7 0.5
Statistical models
NCEP/CPC Markov model 0.7 0.7 0.7 0.6 0.6 0.5 0.5 0.5 0.6
NOAA/CDC Linear Inverse 0.5 0.4 0.3 0.2 0.1 0.1 0 0 0
NCEP/CPC Constructed Analog 0.8 0.7 0.5 0.4 0.3 0.2 0.2 0.2 0.1
NCEP/CPC Can Cor Anal 0.6 0.4 0.4 0.3 0.3 0.4 0.4 0.4 0.5
Landsea/Knaff CLIPER 0.7 0.6 0.5 0.3 0.2 0.2 0.1 0 0
Univ. BC Neural Network 0.7 0.7 0.6 0.6 0.5 0.5 0.5 0.4 0.4
FSU Regression 0.9 0.8 0.7 0.6 0.6 0.6 0.6 0.5 0.6
TCD – UCLA 1.1 1.1 0.9 0.8 0.6 0.4 0.3 0.3 0.3
UNB/CWC Nonlinear PCA 0.7 0.6 0.5 0.4 0.3 0.2 0.2 0.3 0.3
Average, statistical models 0.8 0.7 0.6 0.5 0.4 0.3 0.3 0.3 0.3
Average, all models 0.8 0.7 0.7 0.6 0.6 0.6 0.6 0.5 0.4

Discussion of Current Forecasts

Most of the set of dynamical and statistical model predictions issued during late November and early December 2014 predict weak El Niño conditions through all of northern winter 2014-15 and continuing through much or all of spring 2015. Existence of El Niño conditions appears approximately 80-85% likely for the Dec-Feb 2014-15 season, 70-80% likely for the Jan-Mar and Feb-April 2015 seasons, and drops to 60-70% for Mar-May and Apr-Jun. In the most recent week, the SST anomaly in the Nino3.4 region was 0.9 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 0.49 and 0.85 C for October and November, 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
DJF 2014 ~0% 17% 83%
JFM 2015 ~0% 24% 76%
FMA 2015 ~0% 30% 70%
MAM 2015 ~0% 35% 65%
AMJ 2015 ~0% 39% 61%
MJJ 2015 2% 42% 56%
JJA 2015 5% 41% 54%
JAS 2015 8% 41% 51%
ASO 2015 14% 40% 46%

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

The CPC ENSO forecast is released at 9am (Eastern Time) on the second Thursday of each month.

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.

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.