The central Pacific began to cool again during winter 2011, and from September 2011 models and observations indicated a re-emergence of the La Niña during spring was likely.
The 2011–12 La Niña was relatively late forming, with most indicators only reaching La Niña thresholds by mid-October 2011. This event was not forecast to be as strong as the 2010–11 La Niña, as reflected in seasonal climate outlooks issued at the time. Outlooks indicated a wetter than average spring and early summer for much of northern and eastern Australia, but were not as dramatic as they were during the previous year.
The La Niña consolidated over spring 2011, with many indicators only strengthening slightly during October and early November. The event reached its peak during December 2011 when climate models forecast a return to a neutral ENSO phase during autumn 2012. The 2011–12 La Niña gradually declined over late summer, with some atmospheric indicators continuing to show a La Niña signal during March 2012, while oceanic indicators were generally faster to return to neutral levels. The 2011–12 La Niña concluded in late March 2012.
Monthly sea surface temperature anomalies (difference from normal) in the Pacific Ocean indicate where the ocean is warmer than usual (red) and cooler than usual (blue).
September 2011 – cooling in the central Pacific as the La Niña re-forms
December 2011 – peak of the 2011–12 La Niña; cooler than normal central and eastern Pacific, but not as cool as at the 2010–11 La Niña peak
March 2012 – 2011–12 La Niña has declined; ocean temperatures in the Pacific approach neutral
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The Bureau publishes a regular ENSO Wrap-Up and Model Summary.
These reports contain information about current conditions across the tropical Pacific Ocean, as well as a summary of predictions for ENSO conditions several months ahead from a number of international dynamical climate models, including the Bureau's own model, POAMA (Predictive Ocean Atmosphere Model for Australia).
