Synopsis: Chances increase for El Niño beginning in July-September 2012.
During June 2012, ENSO-neutral continued as reflected in both the oceanic and atmospheric anomalies. However, positive equatorial Pacific sea surface temperature (SST) anomalies have grown, exceeding +0.5oC across the eastern Pacific Ocean by the end of June (Fig. 1). SST anomalies increase moving from the westernmost Niño 4 region to the Niño 1+2 region adjacent to South America, which remained near +1.5oC during the month (Fig. 2). The oceanic heat content anomalies (average temperature in the upper 300m of the ocean) increased during June (Fig. 3), as above-average sub-surface temperatures became more entrenched in the equatorial Pacific (Fig. 4). This warming was consistent with a weakening of the low-level trade winds across the east-central equatorial Pacific, along with a weakening of the persistent pattern of enhanced convection near Papua New Guinea (Fig. 5). The observations are consistent with ENSO-neutral, but reflect a likely progression towards El Niño.
There continues to be a substantial disparity between the statistical and dynamical model SST forecasts for the Niño-3.4 region (Fig. 6). The dynamical models, including the NCEP Climate Forecast System (CFS), largely favor the development of El Niño by July-September 2012, while the majority of statistical models predict ENSO-neutral through the rest of 2012. The forecaster consensus largely favors the dynamical model outcome because those models tend to exhibit greater skill emerging from the Northern Hemisphere "spring barrier" (a period of relatively low confidence ENSO forecasts) and also due to the strengthening of observed signals indicating an evolution towards El Niño. Overall, the forecaster consensus reflects increased chances for El Niño beginning in July-September 2012 (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 Niña are updated monthly in the
Forecast Forum section of CPC's Climate
Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 9 August 2012. To receive
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