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IRI ENSO Forecast

2018 December Quick Look

Published: December 13, 2018

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

El Niño-level SSTs continued to be observed in the November average, and the subsurface waters continued to be warmer than average. However, most atmospheric variables showed ENSO-neutral patterns. The lower-level wind anomalies averaged weakly westerly in the western Pacific, and the equatorial SOI was slightly negative–both suggestions of El Niño. But other indicators were neutral. The official CPC/IRI outlook calls for an 90% chance of El Niño prevailing during winter, and over 60% during spring 2019. An El Niño watch is in effect. The most recent forecasts of statistical and dynamical models collectively show continuing El Niño-level SSTs, most likely weak to moderate in strength, continuing through spring.

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: December 13, 2018

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 Watch

Synopsis: El Niño is expected to form and continue through the Northern Hemisphere winter 2018-19 (~90% chance) and through spring (~60% chance). ENSO-neutral continued during November, despite the continuation of above-average sea surface temperatures (SSTs) across the equatorial Pacific Ocean (Fig. 1). The latest weekly SST indices for all four Niño regions were near +1.0°C (Fig. 2). Positive subsurface temperature anomalies (averaged across 180°-100°W) weakened slightly (Fig. 3), but above-average temperatures persist at depth across the central and eastern equatorial Pacific Ocean (Fig. 4). However, the atmospheric anomalies largely reflected intra-seasonal variability related to the Madden-Julian Oscillation, and have not yet shown a clear coupling to the above-average ocean temperatures. For the month as a whole, atmospheric convection remained close to average near the Date Line and suppressed over Indonesia (Fig. 5). Also, the low-level and upper level winds were mostly near average across the equatorial Pacific.  The equatorial Southern Oscillation index (SOI) was negative, while the traditional SOI was near zero. Despite the above-average ocean temperatures, the overall coupled ocean-atmosphere system remained ENSO-neutral. The majority of models in the IRI/CPC plume predict a Niño3.4 index of +0.5°C or greater to continue through the winter and spring (Fig. 6). The official forecast favors the formation of a weak El Niño, with the expectation that the atmospheric circulation will eventually couple to the anomalous equatorial Pacific warmth.  In summary, El Niño is expected to form and continue through the Northern Hemisphere winter 2018-19 (~90% chance) and spring (~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 10 January 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.

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
NDJ 2018 0% 4% 96%
DJF 2018 0% 9% 91%
JFM 2018 0% 14% 86%
FMA 2018 1% 19% 80%
MAM 2018 2% 28% 70%
AMJ 2018 4% 34% 62%
MJJ 2019 6% 38% 56%
JJA 2019 8% 40% 52%
JAS 2019 9% 42% 49%

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: November 19, 2018

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-November 2018, weak El Niño SST conditions were observed in the NINO3.4 region. The October SST anomaly was 0.86 C, in the weak El Niño range, and for Aug-Oct it was 0.51 C, also indicative of 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 0.8, indicating weak El Niño conditions. However, many of the key atmospheric variables, such as the upper level zonal wind anomalies, the sea level pressure pattern (e.g., the Southern Oscillation index) and the outgoing longwave radiation pattern (convection), have not suggested El Niño conditions, but rather a continuation of ENSO-neutral conditions. The low-level wind anomalies have been westerly during some weeks, but this indication of El Niño has been intermittent. In other words, coupling of the atmosphere to the oceanic conditions has been weak at best. The subsurface temperature anomalies across the eastern equatorial Pacific remain markedly above-average. These warmed waters at depth extend to the surface, resulting in above-average temperatures, and also presaging likely continuation of above-average SST in the coming couple of months. Given the current El Niño-level SST anomalies, the subsurface profile, even with currently poor atmospheric coupling it appears likely that the SST will continue at weak (or greater) El Niño levels into winter and possibly into spring. This expectation assumes that the atmosphere will participate in the event more in the coming month or two.

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 an 80% chance for El Niño during the Dec-Feb season, and 55-60% chance for continuing into spring 2019. An El Niño watch remains active. The latest set of model ENSO predictions, from mid-October, now available in the IRI/CPC ENSO prediction plume, is discussed below. As of mid-November, about than 90% of the dynamical or statistical models predict El Niño conditions from the initial Nov-Jan 2018-19 season through Jan-Mar 2019, with less than 10% showing neutral conditions for this same range of seasons. From Feb-Apr through May-Jul, between 80 and 89% of models continue to predict El Niño. During Jun-Aug and Jul-Sep, between 70 and 75% of models continue to predict El Niño. No model predicts La Niña for any season, with the exception of one model that does so for the Apr-Jun 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% from Nov-Jan through Apr-Jun, rising only to 6% by Jul-Sep. Probabilities for neutral conditions begin at about 5% for Nov-Jan, rise slowly to about 15% for Mar-May, and to about 30% for May-Jul through Jul-Sep.  Probabilities for El Niño, which begin at 95% for Nov-Jan, stay above 90% through Jan-Mar, fall to 85% for Mar-May, and to 61% for Jul-Sep. The failure to drop below 50% by Jul-Sep suggests a possibility for a two-year El Niño event. 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 very strong tilt of the odds toward El Niño conditions from Nov-Jan through Feb-Apr 2019, peaking 95% for Nov-Jan. Probabilities for La Niña are close to zero through Apr-Jun. 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.

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: November 19, 2018

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
NDJ 2018 0% 5% 95%
DJF 2018 0% 6% 94%
JFM 2018 0% 8% 92%
FMA 2018 0% 11% 89%
MAM 2019 0% 15% 85%
AMJ 2019 0% 22% 78%
MJJ 2019 1% 29% 70%
JJA 2019 3% 31% 66%
JAS 2019 6% 33% 61%

 

IRI ENSO Forecast

CPC/IRI Official Probabilistic ENSO Forecast

Published: December 13, 2018

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
NDJ 2018 0% 4% 96%
DJF 2018 0% 9% 91%
JFM 2018 0% 14% 86%
FMA 2018 1% 19% 80%
MAM 2018 2% 28% 70%
AMJ 2018 4% 34% 62%
MJJ 2019 6% 38% 56%
JJA 2019 8% 40% 52%
JAS 2019 9% 42% 49%

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: November 19, 2018

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 (2018 – 2019)
Model NDJ DJF JFM FMA MAM AMJ MJJ JJA JAS
Dynamical Models
NASA GMAO 0.87 0.75 0.47 0.01 -0.39 -0.52 -0.44    
NCEP CFSv2 0.84 0.77 0.69 0.65 0.7 0.78 0.82 0.82  
JMA 1.08 1.12 1.03 0.88 0.77        
BCC_CSM11m 1.32 1.46 1.51 1.47 1.33 1.15 0.99 0.92 0.9
SAUDI-KAU 1.07 1.21 1.28 1.19 1 0.79 0.65 0.64 0.69
LDEO 0.55 0.54 0.64 0.81 0.99 1.16 1.28 1.31 1.27
AUS/POAMA 1.1 1.16 1.11 0.99 0.86 0.8 0.77    
ECMWF 1 1.01 1.01 1.05 1.07        
UKMO 1.18 1.23 1.26 1.26          
KMA SNU 1.23 1.34 1.4 1.4 1.33 1.23 1.15 1.15 1.15
IOCAS ICM 1.02 0.99 0.84 0.68 0.58 0.52 0.46 0.42 0.38
COLA CCSM4 1.15 1.25 1.26 1.21 1.13 1.02 0.92 0.8 0.65
MetFRANCE 0.93 0.98 0.94 0.83 0.74        
SINTEX-F 1.54 1.7 1.72 1.63 1.46 1.29 1.1 0.92 0.72
CS-IRI-MM 0.62 0.39 0.23 0.24 0.21 0.22      
GFDL CM2.1 1.43 1.58 1.59 1.44 1.15 0.86 0.62 0.36 0.11
CMC CANSIP 1.12 1.13 1.08 1.08 1 0.91 0.84 0.79 0.62
GFDL FLOR 1.3 1.31 1.31 1.26 1.17 1.06 1.04 1.03 0.87
Average, Dynamical Models 1.08 1.11 1.08 1.00 0.89 0.80 0.78 0.83 0.74
Statistical Models
PSD-CU LIM 0.87 0.89 0.88 0.81 0.73 0.64 0.56 0.48 0.41
NTU CODA 1.06 1.31 1.12 0.94 1.04 1.38 1.75    
CPC MRKOV 1.12 1.25 1.26 1.17 1.1 1.05 1 0.96 0.98
CPC CA 0.84 0.75 0.59 0.55 0.5 0.51 0.44 0.39 0.25
CSU CLIPR 0.95 0.79 0.64 0.48 0.36 0.25 0.13 0.2 0.28
UBC NNET 1.1 1.22 1.21 1.21 1.2 1.18 1.17 1.15 1.14
FSU REGR 1.16 1.13 0.98 0.81 0.76 0.78 0.77 0.73 0.65
UCLA-TCD 1.04 1.07 1.07 1.03 0.98 0.94 0.94 0.98 1.04
Average, Statistical Models 1.02 1.05 0.97 0.88 0.83 0.84 0.84 0.70 0.68

Discussion of Current Forecasts

Most of the models in the set of dynamical and statistical model predictions issued during mid-November 2018 indicate weak or moderate El Niño conditions for the Nov-Jan season, continuing through winter 2018-19 and into spring 2019. In the most recent week, the SST anomaly in the Nino3.4 region was 0.8 C, in the weak El Niño range, and 0.86 C for the month of October, also indicative of weak Niño. But most key atmospheric variables do not yet reflect El Niño-like conditions, particularly the sea level pressure and convection patterns. The low-level wind anomalies have been weakly westerly, showing weakly an El Niño indication. The subsurface sea temperature anomalies continue to be markedly positive. About 90% of the dynamical and statistical models predict El Niño conditions for the Nov-Jan season, and objective model-based probabilities are more than 90% for Nov-Jan, Dec-Feb and Jan-Mar. Due largely to the lack of ocean-atmosphere coupling, forecasters hedge slightly on this outlook, and judge the probability of El Niño to be about 80% for Dec-Feb. 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
NDJ 2018 0% 5% 95%
DJF 2018 0% 6% 94%
JFM 2018 0% 8% 92%
FMA 2018 0% 11% 89%
MAM 2019 0% 15% 85%
AMJ 2019 0% 22% 78%
MJJ 2019 1% 29% 70%
JJA 2019 3% 31% 66%
JAS 2019 6% 33% 61%

 

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 Dec, 2018