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IRI ENSO Forecast

2017 March Quick Look

Published: March 16, 2017

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 mid-March 2017 the tropical Pacific SST anomaly was mainly in the ENSO-neutral range, but warmer than average SST was observed in the eastern one-third of the basin. Although most of the atmospheric variables across the tropical Pacific are now approximately ENSO-neutral, the pattern of cloudiness, rainfall and winds in the central and western tropical Pacific continues to suggest a borderline La Niña condition. The collection of ENSO prediction models indicates SSTs are likely to remain neutral through spring 2017, with an increasing chance for El Niño development during summer or fall.

Figures 1 and 3 (the official ENSO probability forecast and the objective model-based 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

IRI ENSO Forecast

CPC/IRI ENSO Update

Published: March 9, 2017

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 conditions are favored to continue through at least the Northern Hemisphere spring 2017, with increasing chances for El Niño development into the fall.

ENSO-neutral conditions continued during February, with near-average sea surface temperatures (SSTs) across the central equatorial Pacific and above-average SSTs in the eastern Pacific (Fig. 1). The latest weekly Niño index values were near zero in the Niño-4 and Niño-3.4 regions, and +0.4 and +2.2°C farther east in the Niño-3 and Niño-1+2 regions, respectively (Fig. 2). The upper-ocean heat content anomaly increased during February and was slightly positive when averaged across the central and eastern Pacific (Fig. 3), a reflection of generally above-average temperatures at depth (Fig. 4). Atmospheric convection remained suppressed over the central tropical Pacific and enhanced over the Maritime Continent (Fig. 5). The low-level easterly winds were slightly enhanced over the western tropical Pacific and were weaker than average over the eastern Pacific. Also, upper-level westerly winds were anomalously easterly over portions of the western and eastern Pacific. Overall, the ocean and atmosphere system is consistent with ENSO-neutral conditions.

Most models predict the continuation of ENSO-neutral (3-month average Niño-3.4 index between -0.5°C and 0.5°C) through the early Northern Hemisphere summer (May-July; Fig. 6). However, some dynamical model forecasts, including the NCEP CFSv2, anticipate an onset of El Niño as soon as the late Northern Hemisphere spring (March-May 2017). Because of typically lower skill in forecasts made at this time of the year, and the lingering La Niña-like tropical convection patterns, the forecaster consensus favors ENSO-neutral during the spring (March-May) with a ~75% chance. Thereafter, there are increasing odds for El Niño toward the second half of 2017 (50-55% chance from approximately July-December). In summary, ENSO-neutral conditions are favored to continue through at least the Northern Hemisphere spring 2017, with increasing chances for El Niño development into the fall (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).

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 13 April 2017. 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.

Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
College Park, MD 20740

CPC/IRI Early-Month Official ENSO Forecast Probabilities

Season La Niña Neutral El Niño
FMA 2017 6% 86% 8%
MAM 2017 4% 74% 22%
AMJ 2017 4% 62% 34%
MJJ 2017 6% 53% 41%
JJA 2017 7% 47% 46%
JAS 2017 7% 43% 50%
ASO 2017 8% 40% 52%
SON 2017 10% 37% 53%
OND 2017 11% 36% 53%

Please refer to our licensing agreement for permission to use IRI ENSO materials. The CPC/IRI materials are not included in this licensing.

IRI ENSO Forecast

IRI Technical ENSO Update

Published: March 16, 2017

Note: The SST anomalies cited below refer to the OISSTv2 SST data set, and not ERSSTv4. OISSTv2 is often used for real-time analysis and model initialization, while ERSSTv4 is used for retrospective official ENSO diagnosis because it is more homogeneous over time, allowing for more accurate comparisons among ENSO events that are years apart. During ENSO events, OISSTv2 often shows stronger anomalies than ERSSTv4, and during very strong events the two datasets may differ by as much as 0.5 C. Additionally, the ERSSTv4 may tend to be cooler than OISSTv2, because ERSSTv4 is expressed relative to a base period that is updated every 5 years, while the base period of OISSTv2 is based on a slightly older period and does not account as much for the slow warming trend in the tropical Pacific SST.

Recent and Current Conditions

In March 2017, the NINO3.4 SST anomaly remained in the neutral range, after having been at a borderline or weak La Niña levels during much of the second half of 2016.  For January the SST anomaly was 0.14 C, and for Dec-Feb it was -0.20 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 anomaly in the Nino3.4 region was -0.2, at an ENSO-neutral level. The SST farther east has been maintaining above-average levels for several months, making for a coastal El Niño during the rainy season in coastal Ecuador and northern Peru. Most of the pertinent atmospheric variables have also been assuming neutral patterns, with the exception of the convection anomalies in the central and western tropical Pacific, which have continued to suggest borderline La Niña condtions. The lower-level trade winds and upper level westerly winds have been largely near-average, although there are still weakly enhanced trade winds in the west-central part of the basin. The Southern Oscillation Index (SOI) has been near-average during the last couple of months. Subsurface temperature anomalies across the eastern equatorial Pacific have increased to near to slightly above average. Overall, given the SST and the atmospheric conditions, an ENSO-neutral diagnosis is in order.

Expected Conditions

What is the outlook for the ENSO status going forward? The most recent official diagnosis and outlook was issued one week ago in the NOAA/Climate Prediction Center ENSO Diagnostic Discussion, produced jointly by CPC and IRI; it stated that ENSO-neutral is the most likely condition through northern spring 2017, with increasing chances (50 to 55%) for El Niño development during the summer or fall time frame. The latest set of model ENSO predictions, from mid-March, now available in the IRI/CPC ENSO prediction plume, is discussed below. Those predictions suggest that the SST is most likely to be in the ENSO-neutral range for March-May but with an increased likelihood for El Niño development from summer onward.

As of mid-March, 68% of the dynamical or statistical models predicts neutral ENSO conditions for the initial Mar-May 2017 season, while 32% predicts El Niño conditions and 0% predicts La Niña 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 Jun-Aug 2017 season, among models that do use subsurface temperature information, no model predicts La Niña conditions, 72% predicts El Niño conditions, while 28% predicts neutral ENSO. For all model types, the probabilities for La Niña are 6% or less for for all predicted seasons from Mar-May 2017 through Nov-Jan 2016-17. The probability for El Niño conditions exceeds 50% beginning with Apr-June and lasting throughout the rest of 2017. The chances for El Niño rises to about 55% for Apr-Jun, 65% for May-Jul, between 70% and 75% for Jun-Aug and Jul-Sep, and approximately 80% from Aug-Oct through the final season of Nov-Jan 2017-18. Chances for neutral ENSO conditions drops from near 70% for Mar-May to below 50% thereafter, hovering between 10% and 30% from Jun-Aug through Nov-Jan 2017-18.

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 less than 10% from Mar-May through Oct-Dec 2017, increasing slightly to 11% for Nov-Jan 2017-18. Probabilities for ENSO-neutral are 77% for Mar-May 2017, falling steadily to 40% by May-Jul, and down to near 30% from Jul-Aug through Nov-Jan 2017-18. Probabilities for El Niño are 23% for Mar-May, rise to 45-50% by Apr-Jun and to approximately 60-68% for May-Jul through the final season of Nov-Jan 2017-18. 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.

In summary, the probabilities derived from the models on the IRI/CPC plume describe, on average, a likelihood for neutral ENSO conditions for Mar-May 2017, and more weakly for Apr-Jun. Beginning with May-Jul, El Niño becomes more likely than neutral through the final season of Nov-Jan 2017-18. Although most likely, the chances for El Niño are not overwhelming, reaching approximately two-thirds or slightly higher from Jun-Aug through Nov-Jan 2017-18. Chances for La Niña are very low throughout the forecast period.  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 April 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 36% 30% 34%
JFM 34% 38% 28%
FMA 28% 49% 23%
MAM 23% 56% 21%
AMJ 21% 58% 21%
MJJ 21% 56% 23%
JJA 23% 54% 23%
JAS 25% 51% 24%
ASO 26% 47% 27%
SON 29% 39% 32%
OND 32% 33% 35%
NDJ 35% 29% 36%

 

Please refer to our licensing agreement for permission to use IRI ENSO materials. The CPC/IRI materials are not included in this licensing.

IRI ENSO Forecast

IRI/CPC Model-Based Probabilistic ENSO Forecast

Published: March 16, 2017

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/CPC Mid-Month Model-Based ENSO Forecast Probabilities

Season La Niña Neutral El Niño
MAM 2017 0% 77% 23%
AMJ 2017 0% 53% 47%
MJJ 2017 1% 40% 59%
JJA 2017 2% 32% 66%
JAS 2017 3% 29% 68%
ASO 2017 4% 29% 67%
SON 2017 6% 28% 66%
OND 2017 9% 29% 62%
NDJ 2017 11% 29% 60%

IRI ENSO Forecast

CPC/IRI Official Probabilistic ENSO Forecast

Published: March 9, 2017

The official CPC/IRI 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/IRI 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.



CPC/IRI Early-Month Official ENSO Forecast Probabilities

Season La Niña Neutral El Niño
FMA 2017 6% 86% 8%
MAM 2017 4% 74% 22%
AMJ 2017 4% 62% 34%
MJJ 2017 6% 53% 41%
JJA 2017 7% 47% 46%
JAS 2017 7% 43% 50%
ASO 2017 8% 40% 52%
SON 2017 10% 37% 53%
OND 2017 11% 36% 53%

Please refer to our licensing agreement for permission to use IRI ENSO materials. The CPC/IRI materials are not included in this licensing.

IRI ENSO Forecast

IRI/CPC ENSO Predictions Plume

Published: March 16, 2017

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.


Because of occasional data corrections and late model runs following the time of ENSO product issuance, the data shown in the ENSO forecast table and the ENSO plume graph may not always match. The best source of the ENSO forecast data is http://iri.columbia.edu/~forecast/ensofcst/Data/ensofcst_ALLtoMMYY where MM is the month number and YY is the year.


Seasons (2017-2017)
Model MAM AMJ MJJ JJA JAS ASO SON OND NDJ
Dynamical models
NASA GMAO model 0.3 0.4 0.7 0.9 1.2 1.3 1.5
NCEP CFS version 2 0.3 0.6 0.7 0.8 0.7 0.7 0.8 0.8
Japan Met. Agency model 0.4 0.6 0.6 0.6 0.5
 King Abdulaziz University (Saudi Arabia) CGCM 0.7 0.8 1 1.3 1.6 1.9 2.1 2.1 1.9
Lamont-Doherty model 0.2 0.2 0 -0.2 -0.5 -0.6 -0.6 -0.5 -0.2
POAMA (Austr) model 0.6 0.8 0.9 1.1 1.3 1.4 1.5
ECMWF model 0.4 0.6 0.8 1 1.1
UKMO model 0.7 0.9 1.1 1.3
KMA (Korea) SNU model 0 0 0.1 0.3 0.5 0.6 0.6 0.6 0.6
IOCAS (China) Intermed. Coupled model 0.3 0.6 0.7 0.7 0.8 0.8 0.8 0.8 0.8
COLA CCSM4 model 0.6 0.7 0.9 1.1 1.3 1.4 1.5 1.5 1.6
MÉTÉO FRANCE model 0.3 0.6 0.9 1.3 1.6
CSIR-IRI 3-model MME 0.1 0 -0.1 0.2 0.4 0.7
GFDL CM2.1 Coupled Climate model 0.8 1.1 1.3 1.5 1.6 1.4 1.2 1 0.9
Canadian Coupled Fcst Sys 0.6 0.7 0.9 1.1 1.3 1.4 1.5 1.7 1.9
GFDL CM2.5 FLOR Coupled Climate model 0.5 0.7 0.9 1 1.1 1.1 1.2 1.3 1.3
Average, dynamical models 0.4 0.5 0.7 0.8 0.9 1 1 0.9 0.9
Statistical models
NCEP/CPC Markov model -0.1 -0.1 -0.1 -0.1 -0.2 -0.2 -0.2 -0.2 -0.1
NCEP/CPC Constructed Analog 0.2 0.2 0.1 0.1 0.3 0.3 0.3 0.2 0.1
Landsea/Knaff CLIPER 0.2 0.3 0.5 0.6 0.6 0.7 0.8 0.8 0.8
Univ. BC Neural Network 0.3 0.4 0.5 0.6 0.7 0.7 0.7 0.7 0.6
FSU Regression 0.2 0.3 0.3 0.4 0.5 0.5 0.5 0.6 0.6
TCD – UCLA 0.5 0.7 0.9 1 1.2 1.3 1.4 1.4 1.3
Average, statistical models 0.2 0.3 0.4 0.4 0.5 0.6 0.6 0.6 0.6
Average, all models 0.3 0.5 0.6 0.7 0.8 0.8 0.9 0.8 0.8

Discussion of Current Forecasts

Most of the models in the set of dynamical and statistical model predictions issued during late February and early March 2017 predicts neutral ENSO conditions during the March-May period, but with increasing chances for El Niño development during summer and fall.  In the most recent week, the SST anomaly in the Nino3.4 region was -0.2 C, at a neutral level, and 0.14 C for the month of February, also ENSO-neutral.  The atmospheric variables continue to reflect mainly neutral patterns, except that the pattern of convection and low-level winds over the central and western tropical Pacific continue to suggest borderline La Niña conditions. For northern summer and fall of 2017, the dynamical models tend to favor El Niño development, while the statistical models also do so but with less certainty. 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 Model-Based ENSO Forecast Probabilities

Season La Niña Neutral El Niño
MAM 2017 0% 77% 23%
AMJ 2017 0% 53% 47%
MJJ 2017 1% 40% 59%
JJA 2017 2% 32% 66%
JAS 2017 3% 29% 68%
ASO 2017 4% 29% 67%
SON 2017 6% 28% 66%
OND 2017 9% 29% 62%
NDJ 2017 11% 29% 60%

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.

Please refer to our licensing agreement for permission to use IRI ENSO materials. The CPC/IRI materials are not included in this licensing.

IRI ENSO Forecast

IRI/CPC ENSO Prediction Plumes Based on the North American Multi-model Ensemble (NMME) + Other Comprehensive Dynamical Models

Published:


The three plots on this page show predictions of seasonal (3-month average) sea surface temperature (SST) anomaly in the Niño3.4 region in the east-central tropical Pacific (5°N-5°S, 120°-170°W), covering the nine overlapping seasons beginning with the current month. The predictions are based on most of the models making up the set belonging to the NMME, as well as several other comprehensive coupled dynamical models.

See below for detailed descriptions of the plots.


The first plot (Figure 1) shows the ensemble mean predictions of each of the individual models, and also the average of the individual model predictions (the NMME+). Here, the NMME+ average is not weighted by the number of ensemble members in the individual models. This plot is intended to provide some idea of the disagreement among the individual models.

Predictions of ENSO are probabilistic. The ensemble mean prediction it is only a best single guess. On either side of that prediction, there is a substantial uncertainty distribution, or error tolerance. The second plot (Figure 2) shows the estimated probability distribution of the predictions, showing a set of percentiles within that distribution for each lead time. The distribution is modeled as a normal (Gaussian) distribution, so that the NMME+ forecast represents the center, or 50 percentile, in the distribution. On either side, other percentile values are shown symmetrically, ranging from 1 to 99 and including some intermediate percentiles (5 and 95, 15 and 85, and 25 and 75). The plot enables a user to estimate the probability of the Niño3.4 SST anomaly to be greater or less than some critical value, or within some interval. If, for example, the 85 percentile falls at 1.8° C above average, the probability of the SST exceeding 1.8° C can be estimated at 15%. Probabilities for exceeding or not exceeding values not exactly on percentile line can be roughly interpolated by eye. The overall width of the probability distribution is derived from the historical skill of the hindcasts of the NMME+ models, from 1982 to present, for the specific forecast start time and lead time. This method of defining the probability distribution represents one of two general approaches, the other approach being a direct counting of ensemble members within each of the percentile bands. This second approach assumes that the ensemble spreads of the models are true representations of the uncertainty. One reason the second approach is not used here is that the ensemble spreads may have biases in representing the real world uncertainty. Individual model spreads have often been found to be somewhat narrower than they should be, although in multi-model ensembles this tendency has been shown to be milder or even eliminated. Another reason the ensemble member counting approach is not used here is that there may not be enough ensemble members in the NMME+ to produce a smooth probability distribution, particularly for the relatively detailed percentile bands presented here.

The third plot (Figure 3), sometimes called a spaghetti diagram, shows synthetically generated prediction scenarios that are equally likely. Here, 100 scenarios are shown; any number can be generated for such a diagram. Each scenario is produced using a random number generator, combined with knowledge of the NMME+ forecast and its uncertainty, as well as the amount of persistence of anomalies. The degree of persistence of anomalies is based on the correlation of prediction errors from one lead time to another. In other words, the individual lines are designed to show the correct amount of persistence as expected in nature, rather than jumping around more randomly from one lead time to the next. Sometimes the “spaghetti density” may appear asymmetric about the NMME+ forecast or outside of the 85 and 15 percentile lines. This is purely sampling variability, and would not occur if many thousands of such lines were plotted. But with that many lines, most of the plot would be too crowded to get a sense of the behavior of the lines near the center of the distribution. The main purpose of the diagram is to serve users who want to assess realistic individual scenarios of ENSO behavior rather than statistical summaries of the forecast like the percentiles shown in the second plot.