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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

2019 May Quick Look

Published: May 20, 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

SSTs in the tropical Pacific maintained a weak El Niño level during April and early May, while temperature anomalies of subsurface waters decreased markedly to just slightly above average. Some patterns in the atmosphere show weak El Niño conditions. Collective model forecasts show a continuation of at least weak El Niño-level SSTs lasting through 2019. The official CPC/IRI outlook, with an El Niño advisory, calls for an approximate 70% chance of El Niño continuing during Jun-Aug, decreasing to 55-60% for Sep-Nov.

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: May 9, 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: El Niño Advisory

Synopsis: El Niño is likely to continue through the Northern Hemisphere summer 2019 (70% chance) and fall (55-60% chance).

During April, above-average sea surface temperatures (SSTs) persisted across most of the equatorial Pacific Ocean (Fig. 1), reflecting the ongoing El Niño.  All of the latest weekly Niño indices were near +0.8°C, except for Niño-1+2 index, which was at +0.3°C (Fig. 2). While surface indicators were relatively unchanged during the month, the anomalous upper-ocean subsurface temperatures (averaged across 180°-100°W) decreased through April (Fig. 3). Subsurface temperature anomalies remained positive close to the surface across the equatorial Pacific Ocean, but were increasingly negative at depth (Fig. 4). Suppressed tropical convection was evident near Indonesia and enhanced convection continued near the Date Line, though weaker compared to the last two months (Fig. 5). Low-level wind anomalies were weak over the tropical Pacific Ocean, with easterly anomalies evident over the western Pacific. Upper-level wind anomalies were easterly over the western Pacific and westerly over most of the eastern Pacific.  Overall, oceanic and atmospheric conditions were consistent with El Niño.

The majority of models in the IRI/CPC plume predict El Niño to continue through 2019, with SST anomalies in the Niño-3.4 region clustering between +0.5°C and +1.0°C (Fig. 6). However, model predictions made during the spring tend to be less accurate relative to the rest of the year, so uncertainty remains whether this outcome will occur.  In the shorter term, a recent increase in westerly wind anomalies over the west-central Pacific Ocean portends the possible development of another downwelling oceanic Kelvin wave, which could build up the above-average subsurface temperatures needed for El Niño to persist. In summary,El Niño is likely to continue through the Northern Hemisphere summer 2019 (70% chance) and fall (55-60% 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 13 Jun 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
AMJ 2019 0% 11% 89%
MJJ 2019 0% 20% 80%
JJA 2019 1% 29% 70%
JAS 2019 3% 35% 62%
ASO 2019 5% 35% 60%
SON 2019 7% 35% 58%
OND 2019 9% 33% 58%
NDJ 2019 10% 33% 57%
DJF 2019 10% 33% 57%

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: May 20, 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-May 2019, weak El Niño SST conditions were observed in the NINO3.4 region. The April SST anomaly was 0.82 C, in the weak El Niño range, and for February-April it was 0.84 C, also 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 0.5 C, indicating minimal weak El Niño conditions. Since late January some important atmospheric variables became El Niño-like, including on-and-off westerly low-level zonal wind anomalies and above-average convection near the dateline. In the latest month or two the wind anomalies have weakened to near average (although a new spell of westerly anomalies just appeared in mid-May), while the convection near the dateline has continued. The coupling of the atmosphere to the oceanic conditions is still just adequate to support a weak El Niño. The subsurface temperature anomalies across the eastern equatorial Pacific have been above-average for the past 12 months, but have weakened markedly to just slightly above average in the last month. The waters at depth are still well above average close to the surface in the eastern Pacific, but renewed westerly low-level wind anomalies are needed to reinforce the positive heat content anomaly to allow the weak El Niño to last longer than just one or two more months.

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 gave a 70% chance for El Niño for this northern summer season, dropping to 55-60% for fall season. An El Niño advisory is in effect. The latest set of model ENSO predictions, from mid-May, now available in the IRI/CPC ENSO prediction plume, is next discussed. As of mid-May, 85% of the dynamical or statistical models predict El Niño conditions for the May-Jul season. After May-Jul, the percentage of models forecasting El Niño decreases, dropping to 73% for Jun-Aug and then hovering mainly in the 60-69% range for the longer-lead seasons out to Jan-Mar 2020. No model predicts La Niña for any season.

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 near 0% for May-Jul and Jun-Aug, rising to 9% by Sep-Nov and to near 10% for the farther-out seasons out to Jan-Mar 2020. Probabilities for neutral conditions begin at 20% for May-Jul and rise to the 30-39% range throughout the rest of the forecast seasons out to Jan-Mar 2020. Probabilities for El Niño begin at 80% for May-Jul, thereafter declining to 60% for Jul-Sep and hovering in the 55-59% range for the remainder of the seasons out to Jan-Mar 2020. The failure to drop below 50% throughout 2019 suggests a possibility for a two-year El Niño event, but at this time, even in the second half of the northern spring predictability barrier, there is considerable uncertainty in this possibility. 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 El Niño conditions from May-Jun through Jul-Sep 2019, becoming weaker but still at least 55% through the final Jan-Mar 2020 season. Probabilities for La Niña are close to zero through Jul-Sep. 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: May 20, 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
MJJ 2019 0% 20% 80%
JJA 2019 1% 33% 66%
JAS 2019 3% 37% 60%
ASO 2019 6% 37% 57%
SON 2019 9% 35% 56%
OND 2019 12% 33% 55%
NDJ 2019 11% 33% 56%
DJF 2020 9% 35% 56%
JFM 2020 7% 38% 55%

 

IRI ENSO Forecast

CPC/IRI Official Probabilistic ENSO Forecast

Published: May 9, 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
AMJ 2019 0% 11% 89%
MJJ 2019 0% 20% 80%
JJA 2019 1% 29% 70%
JAS 2019 3% 35% 62%
ASO 2019 5% 35% 60%
SON 2019 7% 35% 58%
OND 2019 9% 33% 58%
NDJ 2019 10% 33% 57%
DJF 2019 10% 33% 57%

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: May 20, 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.


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 MJJ JJA JAS ASO SON OND NDJ DJF JFM
Dynamical Models
NASA GMAO 0.55 0.45 0.46 0.44 0.42 0.34 0.3
NCEP CFSv2 0.91 1.06 1.18 1.09 1.08 1.07 0.93 0.67 0.49
JMA 0.88 0.87 0.81 0.84 0.88
BCC_CSM11m 0.36 0.28 0.34 0.43 0.5 0.56 0.63 0.68 0.71
SAUDI-KAU 0.73 0.7 0.56 0.42 0.32 0.29 0.29 0.33 0.4
LDEO 0.96 0.82 0.56 0.39 0.32 0.21 0.15 0.2 0.4
AUS/POAMA 0.58 0.39 0.26 0.21 0.26 0.33 0.38
ECMWF 0.92 0.87 0.78 0.73 0.79
UKMO 0.86 0.79 0.7 0.67
KMA SNU 0.6 0.68 0.8 0.88 0.89 0.87 0.78 0.69 0.6
IOCAS ICM 0.54 0.56 0.6 0.66 0.74 0.83 0.87 0.79 0.63
COLA CCSM4 0.92 0.81 0.68 0.62 0.62 0.65 0.71 0.79 0.91
MetFRANCE 1.23 1.25 1.16 0.99 0.9
SINTEX-F 0.63 0.43 0.19 0.03 -0.01 -0.01 -0.03 -0.08 -0.14
CS-IRI-MM 0.48 0.4 0.36 0.38 0.45 0.6
GFDL CM2.1 0.99 0.82 0.56 0.38 0.41 0.56 0.74 0.87 0.97
CMC CANSIP 0.94 0.89 0.83 0.77 0.75 0.77 0.83 0.92 0.92
GFDL FLOR 0.8 0.69 0.65 0.67 0.75 0.88 1.04 1.18 1.32
Average, Dynamical Models 0.77 0.71 0.64 0.59 0.59 0.57 0.59 0.64 0.66
Statistical Models
PSD-CU LIM 0.86 0.84 0.78 0.7 0.59 0.49 0.41 0.34 0.28
NTU CODA 1 1.09 1.17 1.26 1.35 1.45 1.45
BCC_RZDM 0.72 0.57 0.42 0.33 0.33 0.37 0.37 0.34 0.31
CPC MRKOV 0.45 0.45 0.48 0.56 0.66 0.76 0.85 0.89 0.82
CPC CA 0.48 0.42 0.39 0.45 0.57 0.69 0.72 0.68 0.6
CSU CLIPR 0.7 0.77 0.84 0.91 0.84 0.78 0.71 0.58 0.46
UBC NNET 0.76 0.73 0.73 0.73 0.73 0.74 0.75 0.76 0.7
FSU REGR 0.63 0.56 0.51 0.51 0.57 0.66 0.7 0.59 0.46
UCLA-TCD 0.61 0.55 0.55 0.57 0.59 0.6 0.6 0.57 0.51
Average, Statistical Models 0.69 0.66 0.65 0.67 0.69 0.73 0.73 0.59 0.52

Discussion of Current Forecasts

Most of the models in the set of dynamical and statistical model predictions issued during mid-May 2019 indicate weak El Niño conditions for the May-Jul season, weakening further but continuing into summer and fall 2019, and not disappearing by late fall. In the most recent week, the SST anomaly in the Nino3.4 region was 0.5 C, at the low end of the weak El Niño range, and 0.82 C for the month of April, in the weak El Niño category. Since late January, some atmospheric variables have also been reflecting El Niño-like conditions. The subsurface sea temperature anomalies remain positive but have weakened considerably from those of a month ago. About 85% of the dynamical and statistical models predict El Niño conditions for the May-Jul season, and objective model-based probabilities are 80% for May-Jul, dropping slowly to about 55% from Aug-Oct through to Jan-Mar 2020. Based on this objective input, forecasters have issued an 80% probability for May-Jul, dropping to 55-60% by autumn. 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
MJJ 2019 0% 20% 80%
JJA 2019 1% 33% 66%
JAS 2019 3% 37% 60%
ASO 2019 6% 37% 57%
SON 2019 9% 35% 56%
OND 2019 12% 33% 55%
NDJ 2019 11% 33% 56%
DJF 2020 9% 35% 56%
JFM 2020 7% 38% 55%

 

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 May, 2019

Our ENSO forecasts are published on the 19th of each month. If the 19th falls on a weekend or holiday, they are released on the closest business day, earlier or later.

The CPC Forecasts are published at 9am on the 2nd Thursday of each month.