ENSO Forecast Navigation

Download the Quicklook PDF

ENSO Forecasts

IRI ENSO Forecast

2015 May Quick Look

Published: May 21, 2015

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 April through mid-May 2015 the SST was at a weak to moderate Niño level. The atmospheric variables also indicate an El Niño pattern, including weakened trade winds, low Southern Oscillation Index and excess rainfall in the central tropical Pacific. The consensus of ENSO prediction models indicate weak to moderate El Niño conditions during the May-July 2015 season in progress, likely strengthening during summer and lasting through 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: May 14, 2015

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 Advisory

Synopsis: There is an approximately 90% chance that El Niño will continue through Northern Hemisphere summer 2015, and a greater than 80% chance it will last through 2015.

By early May 2015, weak to moderate El Niño conditions were reflected by above-average sea surface temperatures (SST) across the equatorial Pacific (Fig. 1) and by the corroborating tropical atmospheric response. The latest weekly Niño indices were +1.2°C in the Niño-4 region, +1.0°C in the Niño-3.4 region, and +1.2°C and +2.3°C in the Niño-3 and Niño-1+2 regions, respectively (Fig. 2). Subsurface temperature anomalies remained substantially above average (Fig. 3) partly in response to a downwelling oceanic Kelvin wave, which resulted in strong positive subsurface anomalies across the central and eastern Pacific (Fig. 4). This anomalous warmth has subsequently persisted in association with El Niño-related ocean-atmosphere coupling. This coupling includes enhanced convection over the central equatorial Pacific (Fig. 5), along with persistent low-level westerly wind anomalies over the western and central equatorial Pacific and persistent upper-level easterly wind anomalies over the central Pacific. Also, the equatorial Southern Oscillation Index (EQSOI) remained negative during the month. Collectively, these features reflect weak to moderate strength El Niño conditions.

Nearly all models predict El Niño (3-month values of the Niño-3.4 index 0.5°C or greater) to continue throughout 2015, and many are also predicting SST anomalies to increase during the next several months (Fig. 6). These forecasts are supported by the continuation of positive subsurface temperature anomalies, enhanced convection near the Date Line, and the persistence of low-level westerly wind anomalies. Given these factors, it is likely that SST anomalies will continue to increase in the coming months. However, model forecast skill tends to be lower during the Northern Hemisphere spring, which somewhat limits confidence in these forecasts. Therefore, there remains considerable uncertainty about how strong this event may become. In summary, there is an approximately 90% chance that El Niño will continue through Northern Hemisphere summer 2015, and a greater than 80% chance it will last through 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 11 June 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
AMJ 2015 ~0% 5% 95%
MJJ 2015 ~0% 7% 93%
JJA 2015 ~0% 10% 90%
JAS 2015 1% 10% 89%
ASO 2015 1% 13% 86%
SON 2015 2% 13% 85%
OND 2015 2% 15% 83%
NDJ 2015 3% 15% 82%
DJF 2015 3% 17% 80%

IRI ENSO Forecast

IRI Technical ENSO Update

Published: May 21, 2015

Recent and Current Conditions

The SST anomaly in the NINO3.4 region has been at a weak El Niño level from late February through mid-May 2015.  For April the average NINO3.4 SST anomaly was 0.78 C, indicative of weak Niño conditions, and for Feb-Apr it was 0.64 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 1.0 C, in the category of weak to low-moderate El Niño.  Accompanying this SST has been an atmospheric pattern with supporting indications of an El Niño condition, including westerly low-level wind anomalies and positive anomalies of convection in the vicinity of the dateline. The Southern Oscillation Index (SOI) and the equatorial SOI have also been indicative of at least weak El Niño conditions.

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 an approximately 90% likelihood for El Niño conditions continuing through summer 2015, and at least 80% to last through the duration of 2015. The latest set of model ENSO predictions, from mid-May, now available in the IRI/CPC ENSO prediction plume, is discussed below. Currently, Nino3.4 SST anomalies are in the weak to moderate El Niño cagtegory. Subsurface temperature anomalies across the eastern equatorial Pacific have been well above average levels during the past 3 months as the downwelling phase of a Kelvin wave has moved eastward at depth in response to westerly low-level wind anomalies during the last 3 to 4 months.  The positive heat content anomaly has promoted increases in SST over the last month, and is likely to lead to further SST increases in the coming few months, depending on the strength and nature of the atmospheric response to the El Niño.  The subsurface heat content, while still substantially above average, has begun decreasing as it has been discharging in the form of far above average SST in the far eastern tropical Pacific. In the atmosphere, the basin-wide sea level pressure anomaly pattern (e.g. the SOI) has been at El Niño levels, and anomalous convection (as measured by OLR) has been above average near the dateline.  Together, the oceanic and atmospheric features reflect the weak to moderate El Niño condition during late April and through mid-May.

As of mid-April, none of the dynamical or statistical models models predicts La Niña or neutral SST conditions for the initial May-Jul 2015 season; 100% predicts El Niño conditions. 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 Aug-Oct 2015 season, among models that do use subsurface temperature information, 95% predicts El Niño SST conditions, 5% predicts ENSO-neutral conditions and none predicts La Niña conditions. For all model types, the probabilities for El Niño are 96% for Jun-Aug, 84% for Jul-Sep, and 88-94% from Aug-Oct through to the beginning of 2016. No models predict La Niña conditions for any forecast period during 2014. Aside from May-Jul and Jun-Aug, when 100% and 96% of models predict El Niño SST conditions, respectively, the season having highest probability for El Niño SST conditions is Dec-Feb 2015-16, when the probability is 94%. (Note that at that long lead time, some of the models do not make forecasts, leaving a smaller set of models.)

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 at 2% or less for all periods from May-Jul through Jan-Mar 2015.  Model probabilities for neutral ENSO conditions are less than 10% for May-Jul and Jun-Aug, rising to 10-15% from Jul-Sep through Sep-Nov, and first exceeding 20% for Jan-Mar 2016. Probabilities for El Niño are 90% or higher from May-Jul to Jul-Sep, 85-89% for Aug-Oct and Sep-Nov 2015, dropping below 80% for the first time by Dec-Feb 2015-16.  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, very high certainty for El Niño conditions for the May-Jul and Jun-Aug seasons, and still high certainty through Sep-Nov. In terms of magnitude, the models suggest strengthening El Niño conditions through northern autumn season, reaching at least moderate strength.  However, model spread is high, reflecting the continued presence of the northern spring ENSO predictability barrier. 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 March 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: May 21, 2015



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

Season La Niña Neutral El Niño
MJJ 2015 ~0% 3% 97%
JJA 2015 ~0% 7% 93%
JAS 2015 ~0% 10% 90%
ASO 2015 1% 11% 88%
SON 2015 1% 12% 87%
OND 2015 2% 16% 82%
NDJ 2015 2% 16% 82%
DJF 2015 2% 19% 79%
JFM 2016 2% 23% 75%

IRI ENSO Forecast

CPC/IRI Consensus Probabilistic ENSO Forecast

Published: May 14, 2015



CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

 

Season La Niña Neutral El Niño
AMJ 2015 ~0% 5% 95%
MJJ 2015 ~0% 7% 93%
JJA 2015 ~0% 10% 90%
JAS 2015 1% 10% 89%
ASO 2015 1% 13% 86%
SON 2015 2% 13% 85%
OND 2015 2% 15% 83%
NDJ 2015 3% 15% 82%
DJF 2015 3% 17% 80%

IRI ENSO Forecast

IRI/CPC ENSO Predictions Plume

Published: May 21, 2015

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 (2015-2016)
Model MJJ JJA JAS ASO SON OND NDJ DJF JFM
Dynamical models
NCEP CFS version 2 1.5 1.9 2.2 2.4 2.7 2.7 2.4 2
NASA GMAO model 1.5 2 2.4 2.7 2.8 2.8 2.8
Japan Met. Agency model 1.2 1.5 1.9 2.3 2.6
Scripps Inst. HCM 0.7 0.7 0.7 0.8 0.8 0.9 0.9 0.9 0.9
Lamont-Doherty model 0.6 0.5 0.3 0.2 0.1 0.1 0.3 0.5 0.7
POAMA (Austr) model 1.5 1.7 1.6 1.6 1.6 1.6 1.6
ECMWF model 1.5 1.8 2.1 2.4 2.7
UKMO model 1.3 1.5 1.7 1.8
KMA (Korea) SNU model 0.8 0.8 0.9 1 1 1 0.9 0.8 0.8
ESSIC Intermed. Coupled model 0.9 0.8 0.7 0.6 0.6 0.7 0.7 0.6 0.4
COLA CCSM3 model 1 1.3 1.4 1.4 1.4 1.5 1.5 1.3 0.9
MÉTÉO FRANCE model 1.3 1.7 1.9 2 2.1
Japan Frontier Coupled model 1.5 1.8 2 2.1 2 2 1.9 1.9 1.6
CSIR-IRI 3-model MME 0.6 0.7 0.8 1 1.2 1.4
GFDL CM2.1 Coupled Climate model 1.5 1.7 1.7 1.6 1.5 1.6 1.5 1.5 1.4
Canadian Coupled Fcst Sys 1.3 1.5 1.7 1.7 1.7 1.8 1.8 1.7 1.5
1.4 1.7 1.9 2 2.1 2.2 2.2 2.1 1.8
Average, dynamical models 1.2 1.4 1.5 1.6 1.7 1.6 1.6 1.3 1.1
Statistical models
NCEP/CPC Markov model 1.1 1.1 1.2 1.4 1.6 1.8 1.9 1.9 1.7
NOAA/CDC Linear Inverse 0.5 0.5 0.5 0.4 0.4 0.4 0.4 0.4 0.4
NCEP/CPC Constructed Analog 0.6 0.6 0.5 0.5 0.7 1 1.1 1 0.8
NCEP/CPC Can Cor Anal 0.8 0.9 0.9 0.9 1 1.1 1.1 0.9 0.7
Landsea/Knaff CLIPER 0.5 0.5 0.5 0.5 0.6 0.7 0.8 0.7 0.5
Univ. BC Neural Network 0.8 0.8 0.9 1 1.1 1.2 1.3 1.4 1.3
FSU Regression 0.9 0.9 0.9 1 1.1 1.3 1.4 1.2 1
TCD – UCLA 1.4 1.6 1.8 2 2.2 2.3 2.3 2.2 1.8
UNB/CWC Nonlinear PCA 1 1 0.9 0.9 0.8 0.6 0.6 0.6 0.7
Average, statistical models 0.8 0.9 0.9 1 1.1 1.2 1.2 1.1 1
Average, all models 1.1 1.2 1.3 1.4 1.5 1.4 1.4 1.2 1

Discussion of Current Forecasts

Most of the set of dynamical and statistical model predictions issued during late April and early May 2015 predict strenthening El Niño SST conditions through northern summer 2015, with El Niño continuing throughout the rest of 2015. Continuation of El Niño conditions appears aat least 90% likely from the current May-Jul 2015 season through to the Jul-Sep seasons, as the average of all models predicts El Niño amplification to at least moderate levels. El Niño probabilities remain over 85% during summer and autumn, and over 80% through the end of 2015, followed by implied dissipation over winter and spring 2015-16. There is still substantial spread among the individual model predictions, dynamical models showing  stronger El Niño predictions than statistical ones. In the most recent week, the SST anomaly in the Nino3.4 region was 1.0 C, reflecting weak to moderate El Niño conditions. Most of the atmospheric variables also reflect El Niño, including lower and upper level wind anomalies, Southern Oscillation Index and the pattern of anomalous convection. The monthly anomalous SSTs in the Niño3.4 region were 0.58 and 0.78 C for March and April, 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
MJJ 2015 ~0% 3% 97%
JJA 2015 ~0% 7% 93%
JAS 2015 ~0% 10% 90%
ASO 2015 1% 11% 88%
SON 2015 1% 12% 87%
OND 2015 2% 16% 82%
NDJ 2015 2% 16% 82%
DJF 2015 2% 19% 79%
JFM 2016 2% 23% 75%

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.