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IRI ENSO Forecast

2014 March Quick Look

Published: March 20, 2014

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)

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During February through mid-March the observed ENSO conditions varied from cool-neutral to the borderline of weak La Niña. However, many of the ENSO prediction models indicate a warming trend, with neutral ENSO during northern spring 2014 and a fairly likely development of weak El Niño conditions by the end of northern summer.

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: March 6, 2014

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

ENSO-neutral is expected to continue through the Northern Hemisphere spring 2014, with about a 50% chance of El Niño developing during the summer or fall.

ENSO-neutral continued during February 2014, with below-average sea surface temperatures (SST) continuing in the eastern equatorial Pacific Ocean and above-average SSTs increasing near the International Date Line (Figure 1). Overall, the weekly Niño indices were variable during the month, with most indices remaining less than -0.5°C (Figure 2). A significant downwelling oceanic Kelvin wave increased the oceanic heat content (Figure 3) and produced large positive subsurface temperature anomalies across the central and east-central Pacific (Figure 4). In addition, toward the end of the month, strong low-level westerly winds re-appeared over the western equatorial Pacific. Convection was suppressed over western Indonesia and the central equatorial Pacific (Figure 5). Collectively, these atmospheric and oceanic conditions reflect ENSO-neutral.

The model predictions of ENSO for this summer and beyond are relatively unchanged from last month. Almost all the models indicate that ENSO-neutral (Niño-3.4 index between -0.5°C and 0.5°C) will persist through the rest of the Northern Hemisphere spring 2014 (Figure 6). While all models predict warming in the tropical Pacific, there is considerable uncertainty as to whether El Niño will develop during the summer or fall. If westerly winds continue to emerge in the western equatorial Pacific, the development of El Niño would become more likely. However, the lower forecast skill during the spring and overall propensity for cooler conditions over the last decade still justify significant probabilities for ENSO-neutral. The consensus forecast is for ENSO-neutral to continue through the Northern Hemisphere spring 2014, with about a 50% chance of El Niño developing during the summer or fall (click CPC/IRI consensus forecast for the chance of each outcome).

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 for the evolution of El Niño/La Niña are updated monthly in the Forecast Forum section of CPC’s Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 10 April 2014. 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 Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
FMA 2014 2% 94% 4%
MAM 2014 3% 84% 13%
AMJ 2014 4% 68% 28%
MJJ 2014 5% 57% 38%
JJA 2014 6% 49% 45%
JAS 2014 7% 44% 49%
ASO 2014 7% 43% 50%
SON 2014 7% 42% 51%
OND 2014 7% 41% 52%

IRI ENSO Forecast

IRI Technical ENSO Update

Published: March 20, 2014

Recent and Current Conditions

The SST anomaly in the Nino3.4 region in recent weeks has been near the borderline between neutral and weak Niña, through mid-March 2014. For February 2014 the Nino3.4 SST anomaly was -0.55 C, indicative of weak La Niña conditions, and for December-February it was -0.37 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 -0.4 C, which is just slightly warmer than the -0.55 C observed in February. The recent borderline weak La Niña conditions are considered a short-lived fluctuation and cannot by themselves be considered a La Niña event.

Expected Conditions

What is the outlook for the ENSO status going forward? The most recent official diagnosis and outlook was issued earlier this month in the NOAA/Climate Prediction Center ENSO Diagnostic Discussion, produced jointly by CPC and IRI; it called for a high likelihood of neutral ENSO conditions enduring into spring 2014, with probabilities of El Niño or La Niña each 40% or less until May-Jul 2014 after which El Niño probabilities rise to 50% by Aug-Oct 2014, and slightly above 50% through autumn 2014. The latest set of model ENSO predictions, from mid-March, now available in the IRI/CPC ENSO prediction plume, is discussed below. Currently, Nino3.4 SST anomalies are in the cool-neutral range. Anomalies are above average in the western part of the basin and somewhat below average in the east-central part of the basin (including the Nino3.4 region). Subsurface temperature anomalies across the central and eastern equatorial Pacific had become below average during January, but during late January and the first half of February had reversed to being slightly above average and currently have increased to more strongly above average levels. A strong Kelvin wave, triggered by two westerly wind events in the western tropical Pacific, is currently traversing the basin and helping increase the subsurface temperature anomaly. In the atmosphere, the basin-wide sea level pressure pattern (e.g. the SOI), had been somewhat as would be found during a weak La Niña during January, but this pattern weakened during February and is now closer to average. The low-level zonal winds have been anomalously westerly in the western tropical Pacific and near average over much of the remainder of the basin. Slightly enhanced westerlies have been observed at upper levels of the atmosphere in a portion of the east-central tropical Pacific. Anomalous convection (as measured by OLR) has been negative in the central tropical Pacific, and positive in the western part of the basin. Together, these features reflect ENSO-neutral conditions. The current Kelvin wave moving toward the South American coast may serve to further increase the subsurface heat content and has the potential to raise the SST in the far eastern part of the basin. This, in turn, could induce anaomlous low level westerlies in the central and eastern part of the equatorial Pacific, which could lead to a coupling of ocean and atmosphere in such a way as to induce the onset of El Niño conditions.

As of mid-March, 4% of the dynamical or statistical models models predicts La Niña SST conditions for the Mar-May 2014 season, none predicts El Niño conditions, and 96% indicates neutral ENSO. 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 2014 season, among models that do use subsurface temperature information, 41% predicts ENSO-neutral SSTs, 59% predicts El Niño conditions and none predicts La Niña conditions. For all model types, the probability for neutral ENSO conditions is above 70% for Mar-May and Apr-Jun 2014, is 67% for May-Jul 2014, and is not far from 30% Jul-Sep through Nov-Jan 2014-15 at the end of the forecast period. Probabilities for El Niño are below 40% through May-Jul 2014, rise to 59% for Jun-Aug, and settle in the 64-73% range from Jul-Sep through Nov-Jan. No model predicts La Niña conditions for any of the 3-month periods between Apr-Jun and Nov-Jan.

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 5% for Mar-May 2014, decreasing to 3-5% through the end of the forecast period in Nov-Jan 2014-15. Model probabilities for neutral ENSO conditions are above 75% for Mar-May and Apr-Jun 2014, 57% for May-Jul, 46% for Jun-Aug, and between 37% and 41% for Jul-Sep through Nov-Jan 2014-15 at the end of the forecast period. Probabilities for El Niño are below 20% through Apr-Jun 2014, rise to 50% for Jun-Aug, near 55% for Jul-Sep, and near 60% for Sep-Nov through Nov-Jan 2014-15. It is clear that the models collectively favor neutral ENSO conditions into northern spring 2014, until around Jun-Aug when El Niño probabilities become competitive with ENSO-neutral probabilities, followed by the remainder of 2014 when El Niño becomes somewhat more likely than neutral.  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, maintenance of neutral ENSO conditions into northern spring 2014. A good possibility for El Niño development is seen starting in Jun-Aug 2014, as the objective model-based probabilities for El Niño begin exceeding those for neutral ENSO through Nov-Jan 2014-15 at the end of the forecast period. The uncertainty will diminish as we progress through the northern spring predictability barrier in the coming two to three months. 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.

 

Climatological Probabilities
Season La Niña Neutral El Niño
DJF 37% 28% 35%
JFM 34% 37% 29%
FMA 30% 48% 22%
MAM 26% 54% 20%
AMJ 24% 54% 22%
MJJ 25% 51% 24%
JJA 25% 50% 25%
JAS 27% 46% 27%
ASO 29% 40% 31%
SON 32% 34% 34%
OND 34% 31% 35%
NDJ 37% 27% 36%

 

IRI ENSO Forecast

IRI/CPC Plume-Based Probabilistic ENSO Forecast

Published: March 20, 2014



IRI/CPC Mid-Month Plume-Based ENSO Forecast Probabilities

Season La Niña Neutral El Niño
MAM 2014 5% 94% 1%
AMJ 2014 5% 78% 17%
MJJ 2014 5% 57% 38%
JJA 2014 4% 46% 50%
JAS 2014 4% 40% 56%
ASO 2014 4% 41% 55%
SON 2014 3% 37% 60%
OND 2014 3% 37% 60%
NDJ 2014 3% 39% 58%

IRI ENSO Forecast

CPC/IRI Consensus Probabilistic ENSO Forecast

Published: March 6, 2014



CPC/IRI Early-Month Consensus ENSO Forecast Probabilities

Season La Niña Neutral El Niño
FMA 2014 2% 94% 4%
MAM 2014 3% 84% 13%
AMJ 2014 4% 68% 28%
MJJ 2014 5% 57% 38%
JJA 2014 6% 49% 45%
JAS 2014 7% 44% 49%
ASO 2014 7% 43% 50%
SON 2014 7% 42% 51%
OND 2014 7% 41% 52%

IRI ENSO Forecast

IRI/CPC ENSO Predictions Plume

Published: March 20, 2014

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 (2014-2014)
Model MAM AMJ MJJ JJA JAS ASO SON OND NDJ
Dynamical models
NCEP CFS version 2 0.1 0.5 0.7 0.8 0.8 0.9 1.1 1.2
NASA GMAO model 0.1 0.3 0.6 0.8 1 1.1 1.2
Japan Met. Agency model 0 0.2 0.4 0.7 0.9
Scripps Inst. HCM 0.2 0.4 0.5 0.6 0.8 1 1.1 1.2 1.2
Lamont-Doherty model -0.2 0 0.2 0.2 0.1 0.2 0.4 0.5 0.4
POAMA (Austr) model -0.2 0.1 0.3 0.5 0.7 0.9 1
ECMWF model 0.2 0.5 0.8 1.1 1.3
UKMO model 0.3 0.5 0.7
KMA (Korea) SNU model 0.1 0.2 0.3 0.5 0.6 0.7 0.8 0.7 0.7
COLA CCSM3 model -0.6 -0.3 0 0.2 0.3 0.3 0.3 0.3 0.3
MÉTÉO FRANCE model -0.1 0.2 0.4 0.8 1
Japan Frontier Coupled model 0 0.2 0.4 0.6 0.6 0.5 0.4 0.3 0.2
CSIR-IRI 3-model MME -0.4 -0.2 0.1 0.2 0.2 0.1
GFDL CM2.1 Coupled Climate model 0.2 0.6 1 1.3 1.3 1 0.8 0.6 0.6
Canadian Coupled Fcst Sys -0.3 -0.1 0.2 0.5 0.7 0.7 0.7 0.7 0.7
Average, dynamical models -0.1 0.2 0.4 0.6 0.7 0.7 0.8 0.7
Statistical models
NCEP/CPC Markov model -0.4 -0.3 -0.2 -0.1 0 0.1 0.3 0.4 0.6
NOAA/CDC Linear Inverse -0.1 -0.1 0 0.1 0.1 0.1 0.2 0.2 0.2
NCEP/CPC Constructed Analog -0.3 -0.1 0.1 0.2 0.1 0.1 0.2 0.4 0.4
NCEP/CPC Can Cor Anal -0.1 0.1 0.4 0.5 0.6 0.7 0.7 0.8 0.7
Landsea/Knaff CLIPER -0.3 -0.2 0 0.1 0.1 0.1 0.1 0.1 0.1
Univ. BC Neural Network -0.2 0 0.1 0.3 0.5 0.6 0.6 0.7 0.7
FSU Regression 0.1 0.6 0.9 1.1 1.1 1.2 1.5 1.8 2
TCD – UCLA -0.1 0.1 0.3 0.4 0.6 0.6 0.6 0.6 0.6
Average, statistical models -0.2 0 0.2 0.3 0.4 0.4 0.5 0.6 0.7
Average, all models -0.1 0.1 0.3 0.5 0.6 0.6 0.7 0.7 0.6

Discussion of Current Forecasts

Most of the set of dynamical and statistical model predictions issued during late February and early March 2014 predict neutral ENSO conditions into northern spring 2014, with a clear warming predicted during late spring and into summer 2014. Development of El Nino conditions appears more than 50% likely by the middle of 2014. In the most recent week, the SST anomaly in the Nino3.4 region was -0.4C, reflecting cool-neutral conditions. 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 Nina, neutral and El Nino 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
MAM 2014 5% 94% 1%
AMJ 2014 5% 78% 17%
MJJ 2014 5% 57% 38%
JJA 2014 4% 46% 50%
JAS 2014 4% 40% 56%
ASO 2014 4% 41% 55%
SON 2014 3% 37% 60%
OND 2014 3% 37% 60%
NDJ 2014 3% 39% 58%

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.