ENSO Alert System Status: La Niña Advisory

Synopsis:  La Niña is favored to develop during August - October 2016, with about a 55-60% chance of La Niña during the fall and winter 2016-17.

ENSO-neutral conditions were observed during the past month, as indicated by near-to-below average surface temperatures (SST) across the eastern equatorial Pacific Ocean (Fig. 1). While the Niño-4 region was slightly above average, the other Niño indices were either slightly below average or near zero during June (Fig. 2). Below-average subsurface temperatures continued (Fig. 3) and extended to the surface in parts of the central and eastern equatorial Pacific (Fig. 4). Atmospheric anomalies over the tropical Pacific Ocean also indicated ENSO-neutral conditions. The traditional Southern Oscillation index was slightly positive while the equatorial Southern Oscillation index was near zero. The upper and lower-level winds were both near average across most of the tropical Pacific. Convection was slightly suppressed over portions of the western tropical Pacific and enhanced over part of Indonesia (Fig. 5). Collectively, these atmospheric and oceanic anomalies reflect ENSO-neutral conditions.

Many models favor La Niña (3-month average Niño-3.4 index less than or equal to -0.5°C) by the end of the Northern Hemisphere summer, continuing during fall and lasting into winter (Fig. 6). Statistical models predict a later onset time (i.e., mid-fall) than dynamical models, and also predict a relatively weaker event. The forecaster consensus is somewhat of a compromise between the two model types, favoring La Niña onset during the August-October season, and predicting a weak event (Niño-3.4 index between -0.5°C and -1.0°C), if an event were to form. Overall, ENSO-neutral conditions currently prevail and La Niña is favored to develop by August - October 2016, with about a 55-60% chance of La Niña during the fall and winter 2016-17 (click 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 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 August 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.