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IRI ENSO Forecast

2019 August Quick Look

Published: August 19, 2019

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

The weak El Niño of 2018-19 has ended, as SSTs in the east-central Pacific cooled to ENSO-neutral levels during July. Patterns in most atmospheric variables also are showing ENSO-neutral conditions. Collective model forecasts favor ENSO-neutral through autumn and winter, but with higher chances for El Niño than La Niña. The official CPC/IRI outlook, no longer carrying an El Niño advisory, generally agrees with the model forecasts through winter.

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: August 8, 2019

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: Last El Niño Advisory

Synopsis: El Niño has transitioned to ENSO-neutral, which is most likely to continue through Northern Hemisphere winter 2019-20 (50-55% chance).

During July, ENSO-neutral conditions were reflected by the combination of below-average sea surface temperatures (SSTs) in the eastern equatorial Pacific Ocean and above-average SSTs in the central Pacific (Fig. 1). The latest weekly ENSO indices were +1.0°C, +0.5°C, -0.2°C and -0.5°C in the Niño-4, Niño-3.4, Niño-3 and Niño-1+2 regions, respectively (Fig. 2). Upper-ocean subsurface temperatures (averaged across 180°-100°W) were near average throughout the month (Fig. 3), as anomalously cool waters prevailed in the eastern Pacific and anomalously warm waters continued in the central Pacific (Fig. 4). Suppressed tropical convection continued over Indonesia, while near-average convection was observed near the Date Line (Fig. 5). Low-level wind anomalies were near average over the tropical Pacific Ocean, and upper-level winds were easterly over the east-central Pacific. The traditional and equatorial Southern Oscillation Indices remained slightly negative. Overall, oceanic and atmospheric conditions were consistent with a transition to ENSO-neutral.

The latest IRI/CPC plume of forecasts of the Niño-3.4 index (Fig. 6) favors ENSO-neutral (Niño-3.4 index between -0.5°C and +0.5°C), with index values greater than zero from late Northern Hemisphere summer into fall, warming closer to the El Niño threshold (+0.5°C) by winter. Atypically, dynamical models forecast weaker positive SST anomalies than statistical models throughout most of the forecast period.  As a result, while forecasters favor ENSO-neutral conditions, the odds of El Niño (~30%) are roughly twice that of La Niña for next winter. In summary, El Niño has transitioned to ENSO-neutral, which is most likely to continue through Northern Hemisphere winter 2019-20 (50-55% chance;  click the 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 12 September 2019. 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 Official ENSO Forecast Probabilities

Season La Niña Neutral El Niño
JAS 2019 2% 68% 30%
ASO 2019 5% 67% 28%
SON 2019 10% 64% 26%
OND 2019 13% 58% 29%
NDJ 2019 16% 54% 30%
DJF 2020 17% 53% 30%
JFM 2020 16% 53% 31%
FMA 2020 15% 54% 31%
MAM 2020 15% 54% 31%

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: August 19, 2019

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 updated every 10 years and so, half of the time, 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 mid-August 2019, warmish but neutral ENSO SST conditions were observed in the NINO3.4 region. The July SST anomaly was 0.41 C, in the upper part of the neutral range, and for May-Jul it was 0.57 C, indicative of a weak El Niño. 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 0.4 C, in the upper portion of the ENSO-neutral range.  From October 2018 to June 2019 borderline or weak El Niño conditions prevailed in the tropical Pacific, but in early July the weekly average SSTs transitioned to a warm-neutral level. SST anomalies have become near-zero or negative in the eastern equatorial Pacific, but remain above-average in the central and west-central part of the basin. Along with this oceanic transition, atmospheric variables have also returned to neutral, including low-level and upper-level zonal wind anomalies and the anomalous convection, which is no longer positive near the dateline. The subsurface temperature anomalies across the eastern equatorial Pacific have been near average over the last two to three months, but with a similar marked contrast between the above-average central Pacific and below-average eastern Pacific.

Expected Conditions

What is the outlook for the ENSO status going forward? The most recent official diagnosis and outlook was issued approximately one week ago in the NOAA/Climate Prediction Center ENSO Diagnostic Discussion, produced jointly by CPC and IRI; it states that current neutral conditions are most likely to continue through the fall and winter. This month the El Niño advisory was terminated. The latest set of model ENSO predictions, from mid-August, now available in the IRI/CPC ENSO prediction plume, is next discussed: As of mid-August, 19% of the dynamical or statistical models predict El Niño conditions for the Aug-Oct season, and 81% predict ENSO-neutral. Going forward, this large probability difference decreases, and from Oct-Dec through Jan-Mar 2020, 45-50% predict neutral and also 45-50% predict El Niño, leaving only about 5% predicting La Niña. Going farther into 2020, probabilities for neutral increasingly exceed those for El Niño.

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 small for all forecast seasons, peaking at 11% for Oct-Dec and Nov-Jan. Probabilities for neutral conditions begin at 73% for Aug-Oct, and drop to 49-55% for Oct-Dec through Mar-May. Probabilities for El Niño begin at 25% for Aug-Oct and rise to near or just above 40% from Oct-Dec through the final season of Apr-Jun 2020. 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 tilt of the odds toward neutral ENSO conditions for the entire forecast period of Aug-Oct through Mar-May 2020, with El Niño most competitive from Nov-Jan onward when it hovers at slightly over 40%. Probabilities for La Niña are no higher than 11% 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 early next month by CPC and IRI, which will include some human judgment in combination with the model guidance.

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: August 19, 2019

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
ASO 2019 2% 73% 25%
SON 2019 8% 59% 33%
OND 2019 11% 50% 39%
NDJ 2019 11% 48% 41%
DJF 2020 10% 49% 41%
JFM 2020 6% 51% 43%
FMA 2020 4% 55% 41%
MAM 2020 2% 55% 43%
AMJ 2020 3% 57% 40%

 

IRI ENSO Forecast

CPC/IRI Official Probabilistic ENSO Forecast

Published: August 8, 2019

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
JAS 2019 2% 68% 30%
ASO 2019 5% 67% 28%
SON 2019 10% 64% 26%
OND 2019 13% 58% 29%
NDJ 2019 16% 54% 30%
DJF 2020 17% 53% 30%
JFM 2020 16% 53% 31%
FMA 2020 15% 54% 31%
MAM 2020 15% 54% 31%

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: August 19, 2019

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.


Notice about the NASA-GMAO model ENSO forecasts

GMAO staff discovered a mistake in the calculation of ensemble mean fields that resulted in an under-representation of ensemble spread and an over-representation of error in the ensemble mean. The mistake impacts forecasts from Feb 2017 to the present, and has been corrected as of August 2019. All forecasts hence will have the correct fields. We have not corrected any previous forecast output sent to IRI. If you need the retroactive corrected fields, please contact GMAO at: anna.borovikov@nasa.gov, kazumi.nakada@nasa.gov


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 (2019 – 2020)
Model ASO SON OND NDJ DJF JFM FMA MAM AMJ
Dynamical Models
NASA GMAO -0.21 -0.52 -0.8 -0.99 -1.07 -1.04 -0.96
NCEP CFSv2 -0.01 -0.04 -0.11 -0.28 -0.39 -0.31 -0.07 0.24
JMA -0.05 -0.05 -0.03 -0.06 -0.07
BCC_CSM11m 0.26 0.34 0.5 0.62 0.68 0.69 0.69 0.69 0.65
SAUDI-KAU -0.09 -0.05 -0.06 -0.11 -0.04 0.17 0.38 0.45 0.43
LDEO 0.6 0.6 0.59 0.68 0.85 0.96 0.86 0.61 0.33
AUS/ACCESS 0.23 0.23 0.27 0.33
ECMWF 0.07 0.06 0.13 0.09 0
UKMO 0.16 0.14 0.2 0.24
KMA SNU 0.06 0.06 0.12 0.17 0.19 0.18 0.16 0.14 0.12
IOCAS ICM 0.51 0.54 0.59 0.61 0.52 0.39 0.28 0.21 0.14
COLA CCSM4 0.08 -0.08 -0.19 -0.24 -0.24 -0.12 0.08 0.27 0.41
MetFRANCE 0.01 -0.08 -0.06 -0.06 -0.03
SINTEX-F 0.35 0.44 0.54 0.6 0.58 0.52 0.45 0.41 0.37
CS-IRI-MM 0.3 0.45 0.67 0.84 0.91 0.92
GFDL CM2.1 -0.11 -0.11 0.06 0.19 0.28 0.4 0.5 0.53 0.49
CMC CANSIP 0.04 -0.04 -0.03 -0.02 0 0.06 0.13 0.14 0.13
GFDL FLOR 0.35 0.43 0.52 0.61 0.7 0.8 0.88 0.93 0.89
Average, Dynamical Models 0.14 0.13 0.16 0.18 0.18 0.28 0.28 0.42 0.40
Statistical Models
NTU CODA 0.75 0.76 0.77 0.78 0.79 0.79 0.77
BCC_RZDM 0.64 0.75 0.84 0.86 0.77 0.61 0.41 0.16 -0.07
CPC MRKOV 0.33 0.45 0.58 0.7 0.77 0.75 0.67 0.59 0.55
CPC CA 0.46 0.63 0.8 0.83 0.76 0.66 0.62 0.56 0.54
CSU CLIPR 0.29 0.44 0.58 0.73 0.6 0.46 0.33 0.25 0.16
IAP-NN 0.6 0.68 0.74 0.79 0.82 0.87 0.9 0.91 0.91
UBC NNET 0.49 0.52 0.5 0.47 0.44 0.39 0.34 0.29 0.22
UCLA-TCD 0.37 0.37 0.38 0.39 0.37 0.33 0.29 0.25 0.22
Average, Statistical Models 0.49 0.58 0.65 0.69 0.67 0.61 0.54 0.43 0.36

Discussion of Current Forecasts

Many of the models in the set of dynamical and statistical model predictions issued during mid-August 2019 show currently above-average but ENSO-neutral conditions continuing through the fall and into winter, while a somewhat smaller number of models show weak El Niño conditions redeveloping by late fall. Very few models predict La Niña. In the most recent week, the SST anomaly in the Nino3.4 region was 0.4 C, in the high portion of the ENSO-neutral range, and 0.41 C for the month of July, in the ENSO-neutral category. The subsurface sea temperature anomalies are also close to average. About 80% of the dynamical and statistical models predict neutral conditions for the Aug-Oct season, and objective model-based probabilities are 73% for neutral for Aug-Oct, dropping to near 50% by winter as probabilities for El Niño slowly rise to 40-45% from late fall through winter. Based on the multi-model mean prediction, 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
ASO 2019 2% 73% 25%
SON 2019 8% 59% 33%
OND 2019 11% 50% 39%
NDJ 2019 11% 48% 41%
DJF 2020 10% 49% 41%
JFM 2020 6% 51% 43%
FMA 2020 4% 55% 41%
MAM 2020 2% 55% 43%
AMJ 2020 3% 57% 40%

 

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

Forecast Probability Distribution Based on the IRI/CPC ENSO Prediction Plume

Models not available yet for Aug, 2019