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CPC/IRI ENSO Update

08 Aug 2013

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: Not Active

Synopsis: ENSO-neutral is favored into the Northern Hemisphere fall 2013.

ENSO-neutral conditions persisted during July 2013, as reflected by near-average sea surface temperatures (SSTs) across the central and east-central equatorial Pacific and below-average SSTs in the eastern Pacific (Fig. 1). Consistent with this pattern, weekly Niño-4 and Niño-3.4 values were between -0.5° and 0°C, while Niño-3 and Niño-1+2 indices remained cooler than -0.5°C (Fig. 2). The oceanic heat content (average temperature in the upper 300m of the ocean) anomalies continued to be slightly above average during July (Fig. 3), due to the persistence of above-average sub-surface temperatures in most of the eastern half of the Pacific (Fig. 4). The low-level winds remained near average across the equatorial Pacific, while weak upper-level westerly anomalies persisted in the western Pacific. Convection continued to be enhanced over Indonesia and suppressed in the central part of the basin (Fig. 5). Collectively, these atmospheric and oceanic conditions reflect ENSO-neutral.

Most model forecasts continue to predict ENSO-neutral (Niño-3.4 index between -0.5°C and 0.5°C) into the Northern Hemisphere spring 2014 (Fig. 6). The statistical model forecasts remain cooler in the Niño-3.4 region relative to the dynamical model forecasts. Similar to last month, the forecast consensus favors ENSO-neutral (60% chance or greater) through October – December 2013 (see CPC/IRI consensus forecast).

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 Niño are updated monthly in the Forecast Forum section of CPC's Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 5 Sep 2013. 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.