IRI ENSO Forecast

IRI ENSO Forecast
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:

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%        48%

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