IRI ENSO Forecast
2015 December Quick Look
Published: December 10, 2015
A monthly summary of the status of El Niño, La Niña, and the Southern Oscillation, or ENSO, based on the NINO3.4 index (120-170W, 5S-5N)
Use the navigation menu on the right to navigate to the different forecast sections
During early December 2015 the tropical Pacific SST was at a strong El Niño level. All atmospheric variables strongly support the El Niño pattern, including weakened trade winds and excess rainfall in the east-central tropical Pacific. The consensus of ENSO prediction models indicate continuation of strong El Niño conditions during the December-February 2015-16 season in progress. Further strengthening is possible, but not likely, into mid-winter 2015-16, with the event slowly weakening during spring 2016.
Historically Speaking
- El Niño and La Niña events tend to develop during the period Apr-Jun and they
- Tend to reach their maximum strength during Dec-Feb
- Typically persist for 9-12 months, though occasionally persisting for up to 2 years
- Typically recur every 2 to 7 years
Figure 1 is based on a consensus of CPC and IRI forecasters, in association with the official CPC/IRI ENSO Diagnostic Discussion
Figure 3 is purely objective, based on regression, using equally weighted model predictions from the plume
IRI ENSO Forecast
CPC/IRI ENSO Update
Published: December 10, 2015
El Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued jointly by the Climate Prediction Center/NCEP/NWS and the International Research Institute for Climate and Society
ENSO Alert System Status: El Niño Advisory
Synopsis: El Niño is expected to remain strong through the Northern Hemisphere winter 2015-16, with a transition to ENSO-neutral anticipated during late spring or early summer 2016.
A strong El Niño continued during November as indicated by well above-average sea surface temperatures (SSTs) across the central and eastern equatorial Pacific Ocean (Fig. 1). The Niño-4, Niño-3.4 and Niño-3 indices rose to their highest levels so far during this event, while the Niño-1+2 index remained approximately steady (Fig. 2). The subsurface temperatures in the central and eastern Pacific, while still well above average, decreased slightly ((Figs. 3) due to the eastward push of the upwelling phase of an equatorial oceanic Kelvin wave (Fig. 4). Low-level westerly wind anomalies and upper-level easterly wind anomalies continued over the most of the tropical Pacific. The traditional and equatorial Southern Oscillation Index (SOI) values remained negative. These conditions are associated with enhanced convection over the central tropical Pacific and suppressed convection over Indonesia (Fig. 5).Collectively, these atmospheric and oceanic anomalies reflect a strong El Niño episode that has matured.
Most models indicate that a strong El Niño will continue through the Northern Hemisphere winter 2015-16, followed by weakening and a transition to ENSO-neutral during the late spring or early summer (Fig. 6). The forecaster consensus remains nearly unchanged from last month, with the expectation that this El Niño will rank among the three strongest episodes as measured by the 3-month SST departures in the Niño 3.4 region dating back to 1950. El Niño is expected to remain strong through Northern Hemisphere winter 2015-16, with a transition to ENSO-neutral anticipated during the late spring or early summer 2016 (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).
El Niño has already produced significant global impacts. and is expected to affect temperature and precipitation patterns across the United States during the upcoming months (the 3-month seasonal outlook will be updated on Thursday December 17th). Seasonal outlooks indicate an increased likelihood of above-median precipitation across the southern tier of the United States, and below-median precipitation over the northern tier of the United States. Above-average temperatures are favored in the West and northern half of the country with below-average favored in the southern Plains and along the Gulf Coast.
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 14 January 2016. 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 Consensus ENSO Forecast Probabilities
| Season | La Niña | Neutral | El Niño |
|---|---|---|---|
| NDJ 2015 | ~0% | ~0% | 100% |
| DJF 2016 | ~0% | ~0% | 100% |
| JFM 2016 | ~0% | 1% | 99% |
| FMA 2016 | 1% | 5% | 94% |
| MAM 2016 | 1% | 14% | 85% |
| AMJ 2016 | 5% | 35% | 60% |
| MJJ 2016 | 13% | 48% | 39% |
| JJA 2016 | 21% | 53% | 26% |
| JAS 2016 | 31% | 49% | 20% |
IRI ENSO Forecast
IRI Technical ENSO Update
Published: November 19, 2015
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 between ENSO events that are years apart. During ENSO events, OISSTv2 usually shows stronger anomalies than ERSSTv4, and during very strong events the two datasets may differ by as much as 0.5 C. Therefore, the anomalies cited below for this strong 2015-16 event are likely larger than those that will later be cited officially, particularly in comparisons with other strong El Niño events like 1997-98 and 1982-83.
Recent and Current Conditions
The SST anomaly in the NINO3.4 region attained a weak El Niño level beginning late February 2015, strengthened to moderate strength around mid-May, and strengthened further to a strong level beginning around mid-July. For October the average NINO3.4 SST anomaly was 2.46 C, indicative of strong El Niño conditions, and for Aug-Oct it was 2.27 C. The IRI’s definition of El Niño, like NOAA/Climate Prediction Center’s, requires that the SST anomaly in the Nino3.4 region (5S-5N; 170W-120W) exceed 0.5 C. Similarly, for La Niña, the anomaly must be -0.5 C or less. The climatological probabilities for La Niña, neutral, and El Niño conditions vary seasonally, and are shown in a table at the bottom of this page for each 3-month season. The most recent weekly SST anomaly in the Nino3.4 region was 3.0 C, in the category of strong El Niño. Accompanying this SST has been a clear and strong El Niño atmospheric pattern, including westerly low-level wind anomalies and positive anomalies of convection near and east of the dateline. The Southern Oscillation Index (SOI) and the equatorial SOI have also been quite negative, indicative of El Niño conditions.
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 called for this strong El Niño to peak during this 2015-16 winter, then dissipate to neutral during late spring or early summer 2016. The latest set of model ENSO predictions, from mid-Nov, now available in the IRI/CPC ENSO prediction plume, is discussed below. Currently, besides weekly Nino3.4 SST anomalies being in the strong El Niño category, subsurface temperature anomalies across the eastern equatorial Pacific have been at well above average levels. The strong positive heat content anomaly has promoted steady increases in SST over the last 5 months, and may lead to smaller further SST increases in the coming one to two months, depending on the strength and nature of the atmospheric-oceanic feedbacks. In the atmosphere, the basin-wide sea level pressure anomaly pattern (e.g. the SOI) has been clearly at El Niño levels. Anomalous convection (as measured by OLR) has been above average both near and just east of the dateline. Together, the oceanic and atmospheric features reflect strong El Niño conditions for late October through mid-November.
As of mid-November, none of the dynamical or statistical models models predicts La Niña or neutral SST conditions for the initial Nov-Jan 2015-16 season; 100% predicts El Niño conditions. At lead times of 3 or more months into the future, statistical and dynamical models that incorporate information about the ocean’s observed subsurface thermal structure generally exhibit higher predictive skill than those that do not. For the Feb-Apr 2016 season, among models that do use subsurface temperature information, 100% predicts El Niño SST conditions, while none predicts ENSO-neutral conditions and none predicts La Niña conditions. For all model types, the probabilities for El Niño are near 100% (i.e., higher than 99.5%) for Nov-Jan 2015-16 through Feb-Apr 2016, dropping to 96% for Mar-May and down to 52% by May-Jul and lower thereafter. No model predicts La Niña conditions for any forecast period through May-Jul 2016, rising to 28 for Jul-Sep. Chances for neutral ENSO conditions are near 0% through Feb-Apr 2016, 4% for Mar-May and 48% for May-Jul 2016.
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-zero from Nov-Jan 2015-16 through Apr-Jun 2016, and up to 28% by Jul-Sep 2016. Model probabilities for neutral ENSO conditions are less than 5% through Mar-May 2016, 23% for Apr-Jun and near 50% for Jun-Aug and Jul-Sep 2016. Probabilities for El Niño are near 100% from Nov-Jan 2015-16 to Feb-Apr 2016, 97% for Mar-May, and down to 50% and 21% for May-Jul and Jul-Sep, respectively. A plot of the probabilities generated from this most recent IRI/CPC ENSO prediction plume using the multi-model mean and the Gaussian standard error method summarizes the model consensus out to about 10 months into the future. The same cautions mentioned above for the distributional count of model predictions apply to this Gaussian standard error method of inferring probabilities, due to differing model biases and skills. In particular, this approach considers only the mean of the predictions, and not the total range across the models, nor the ensemble range within individual models.
The probabilities derived from the models on the IRI/CPC plume describe, on average, extremely high certainty for El Niño conditions for the Nov-Jan 2015-16 through Mar-May 2016 seasons. In terms of magnitude, the models suggest strengthening El Niño conditions through early northern winter season, which is nearly upon us, nearly definitely peaking at the level of strong El Niño. Model forecast spread still exists, and peak event strength could range from about 1.8 to 2.8 C with a slight possibility of being outside of that interval on either side. 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 October by CPC and IRI, which will include some human judgement in combination with the model guidance.
| 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% |
IRI ENSO Forecast
IRI/CPC Plume-Based Probabilistic ENSO Forecast
Published: November 19, 2015
IRI/CPC Mid-Month Plume-Based ENSO Forecast Probabilities
| Season | La Niña | Neutral | El Niño |
|---|---|---|---|
| NDJ 2015 | ~0% | ~0% | 100% |
| DJF 2016 | ~0% | ~0% | 100% |
| JFM 2016 | ~0% | ~0% | 100% |
| FMA 2016 | ~0% | ~0% | 100% |
| MAM 2016 | ~0% | 3% | 97% |
| AMJ 2016 | ~0% | 23% | 77% |
| MJJ 2016 | 7% | 43% | 50% |
| JJA 2016 | 17% | 52% | 31% |
| JAS 2016 | 28% | 51% | 21% |
IRI ENSO Forecast
CPC/IRI Consensus Probabilistic ENSO Forecast
Published: December 10, 2015
CPC/IRI Early-Month Consensus ENSO Forecast Probabilities
| Season | La Niña | Neutral | El Niño |
|---|---|---|---|
| NDJ 2015 | ~0% | ~0% | 100% |
| DJF 2016 | ~0% | ~0% | 100% |
| JFM 2016 | ~0% | 1% | 99% |
| FMA 2016 | 1% | 5% | 94% |
| MAM 2016 | 1% | 14% | 85% |
| AMJ 2016 | 5% | 35% | 60% |
| MJJ 2016 | 13% | 48% | 39% |
| JJA 2016 | 21% | 53% | 26% |
| JAS 2016 | 31% | 49% | 20% |
IRI ENSO Forecast
IRI/CPC ENSO Predictions Plume
Published: November 19, 2015
Note on interpreting model forecasts
The following graph and table show forecasts made by dynamical and statistical models for SST in the Nino 3.4 region for nine overlapping 3-month periods. Note that the expected skills of the models, based on historical performance, are not equal to one another. The skills also generally decrease as the lead time increases. Thirdly, forecasts made at some times of the year generally have higher skill than forecasts made at other times of the year--namely, they are better when made between June and December than when they are made between February and May. Differences among the forecasts of the models reflect both differences in model design, and actual uncertainty in the forecast of the possible future SST scenario.
| Seasons (2015-2016) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Model | NDJ | DJF | JFM | FMA | MAM | AMJ | MJJ | JJA | JAS |
| Dynamical models | |||||||||
| NASA GMAO model | 2.8 | 2.8 | 2.6 | 2.2 | 1.8 | 1.1 | 0.5 | ||
| NCEP CFS version 2 | 2.5 | 2.2 | 1.9 | 1.7 | 1.5 | 1.2 | 0.9 | 0.6 | |
| Japan Met. Agency model | 2.4 | 2 | 1.5 | 1.1 | 0.9 | ||||
| Scripps Inst. HCM | 2.5 | 2.4 | 2.1 | 1.7 | 1.1 | 0.5 | -0.1 | -0.7 | -1.2 |
| Lamont-Doherty model | 2.6 | 2.5 | 2.5 | 2.3 | 2 | 1.6 | 1.3 | 1.1 | 1.1 |
| POAMA (Austr) model | 2.7 | 2.4 | 2 | 1.6 | 1.2 | 0.9 | 0.5 | ||
| ECMWF model | 2.6 | 2.4 | 2 | 1.5 | 1 | ||||
| UKMO model | 2.9 | 2.7 | 2.4 | 2 | |||||
| KMA (Korea) SNU model | 1.7 | 1.6 | 1.5 | 1.3 | 1.2 | 1 | 0.7 | 0.5 | 0.3 |
| IOCAS (China) Intermed. Coupled model | 2.7 | 2.5 | 2.1 | 1.6 | 1.2 | 0.8 | 0.4 | 0.1 | -0.1 |
| COLA CCSM3 model | 3.1 | 3.2 | 3 | 2.6 | 2 | 1.4 | 0.7 | 0 | -0.5 |
| MÉTÉO FRANCE model | 2.4 | 2 | 1.6 | 1.2 | 0.9 | ||||
| Japan Frontier Coupled model | 2.7 | 2.4 | 2.1 | 1.9 | 1.6 | 1.1 | 0.6 | 0.2 | 0 |
| CSIR-IRI 3-model MME | 2.1 | 1.9 | 1.6 | 1.2 | 0.6 | 0.1 | |||
| GFDL CM2.1 Coupled Climate model | 3.1 | 3 | 2.7 | 2.3 | 1.7 | 1.1 | 0.5 | -0.2 | -0.6 |
| Canadian Coupled Fcst Sys | 2.7 | 2.6 | 2.1 | 1.7 | 1.2 | 0.7 | 0.1 | -0.3 | -0.5 |
| GFDL CM2.5 FLOR Coupled Climate model | 2.8 | 2.5 | 2.2 | 1.8 | 1.3 | 0.7 | -0.1 | -0.8 | -1.3 |
| Average, dynamical models | 2.6 | 2.4 | 2.1 | 1.7 | 1.3 | 0.9 | 0.5 | 0 | -0.3 |
| Statistical models | |||||||||
| NCEP/CPC Markov model | 2.6 | 2.5 | 2.2 | 1.9 | 1.5 | 1.2 | 1 | 0.7 | 0.6 |
| NOAA/CDC Linear Inverse | 1.5 | 1.2 | 0.9 | 0.6 | 0.4 | 0.2 | 0 | -0.1 | -0.2 |
| NCEP/CPC Constructed Analog | 3 | 2.8 | 2.3 | 1.7 | 1.1 | 0.6 | 0.1 | -0.3 | -0.4 |
| NCEP/CPC Can Cor Anal | 2.4 | 2 | 1.6 | 1.2 | 1 | 0.7 | 0.4 | 0.2 | 0 |
| Landsea/Knaff CLIPER | 2.5 | 2.1 | 1.7 | 1.3 | 0.9 | 0.6 | 0.2 | 0.1 | 0.1 |
| Univ. BC Neural Network | 2.4 | 2.4 | 2.2 | 2 | 1.8 | 1.5 | 1.2 | 1 | 0.7 |
| FSU Regression | 2.7 | 2.5 | 2.1 | 1.6 | 1.1 | 0.5 | 0 | -0.4 | -0.5 |
| TCD – UCLA | 2.7 | 2.6 | 2.3 | 1.9 | 1.6 | 1.2 | 1 | 0.9 | 0.8 |
| UNB/CWC Nonlinear PCA | 1.8 | 1.6 | 1.2 | 1 | 0.8 | 0.7 | 0.6 | 0.5 | 0.5 |
| Average, statistical models | 2.4 | 2.2 | 1.8 | 1.5 | 1.1 | 0.8 | 0.5 | 0.3 | 0.2 |
| Average, all models | 2.5 | 2.3 | 2 | 1.6 | 1.2 | 0.9 | 0.5 | 0.2 | -0.1 |
Discussion of Current Forecasts
Most of the set of dynamical and statistical model predictions issued during late October and early November 2015 predict just slight further strengthening El Niño SST conditions into later fall 2015 or early winter 2015-16, with El Niño continuing well into spring 2016. Continuation of El Niño conditions appears at least 99% likely from the current Nov-Jan 2015-16 season through to the Feb-Apr 2015-16 season. The average of all models predicts maintenance of strong El Niño levels (the level that has been attained since July), with only one predicting immediate weakening from current observed levels. El Niño probabilities remain over 90% into spring 2016, and fall rapidly to about 50% by May-July 2016 and lower thereafter. Many models predict peak SST anomaly values between 1.8 and 2.8C, although just a few are outside of that interval on either side. In the most recent week, the SST anomaly in the Nino3.4 region was 3.0 C, reflecting strong El Niño conditions in this weekly time scale, and 2.5 C for the month of September, also at a strong level. All of the atmospheric variables also reflect El Niño, including lower and upper level wind anomalies, the Southern Oscillation Index and the pattern of anomalous convection. Based on the multi-model mean predictions, and the expected skill of the models by start time and lead time, the probabilities (X100) for La Niña, neutral and El Niño conditions (using -0.5C and 0.5C thresholds) over the coming 9 seasons are:
IRI/CPC Mid-Month Plume-Based ENSO Forecast Probabilities
| Season | La Niña | Neutral | El Niño |
|---|---|---|---|
| NDJ 2015 | ~0% | ~0% | 100% |
| DJF 2016 | ~0% | ~0% | 100% |
| JFM 2016 | ~0% | ~0% | 100% |
| FMA 2016 | ~0% | ~0% | 100% |
| MAM 2016 | ~0% | 3% | 97% |
| AMJ 2016 | ~0% | 23% | 77% |
| MJJ 2016 | 7% | 43% | 50% |
| JJA 2016 | 17% | 52% | 31% |
| JAS 2016 | 28% | 51% | 21% |
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.
