SST Anomaly

2009-12-08T01:49:00.005-07:00

El nino/Lanina 2011/2012

2009-12-08T01:23:00.046-07:00

EL NIÑO/SOUTHERN OSCILLATION (ENSO)

DIAGNOSTIC DISCUSSION

issued by
CLIMATE PREDICTION CENTER/NCEP
and the International Research Institute for Climate and Society

9 February 2012

ENSO Alert System Status: La Niña Advisory

Spanish Version

Synopsis: La Niña is likely to transition to ENSO-neutral conditions during March-May 2012.

A mature La Niña continued during January 2012, as below-average sea surface temperatures (SST) persisted across the equatorial Pacific Ocean (Fig. 1). The weekly SST indices remained near -1.0^oC in the Niño-3.4 and Niño-4 regions (Fig. 2). However, the negative SST anomalies weakened in the far eastern Pacific, indicated by warming in the Niño-1+2 and Niño-3 regions. The oceanic heat content (average temperature in the upper 300m of the ocean) anomalies also weakened slightly (Fig. 3), but continued to reflect an extensive area of below-average subsurface temperatures east of the Date Line (Fig. 4). Also, anomalous low-level easterly and upper-level westerly winds persisted over the central and west-central Pacific. Convection remained suppressed in the western and central Pacific, and enhanced over Indonesia (Fig. 5). Collectively, the oceanic and atmospheric patterns reflect a weak-to-moderate strength La Niña.

A majority of models predict La Niña to weaken through the rest of the Northern Hemisphere winter 2011-12, and then to dissipate during the spring 2012 (Fig. 6). Also, there is evidence of a downwelling phase of an eastward-propagating oceanic Kelvin wave (red shading, Fig. 4), which may increase temperatures across the Pacific in the next couple of months. The combination of a weakening subsurface temperature anomaly, the historical seasonal evolution, and forecaster preference for the average dynamical model prediction favors a return to ENSO-neutral conditions during the Northern Hemisphere spring, which are likely to continue into the summer. Therefore La Niña is likely to transition to ENSO-neutral conditions during March-May 2012 (see CPC/IRI consensus forecast).

Because the strength of impacts in the United States is not necessarily related to the exact strength of La Niña in the tropical Pacific, we expect La Niña impacts to continue even as the episode weakens. Over the U.S. during February - April 2012, there is an increased chance of above-average temperatures across the south-central and southeastern U.S., and below-average temperatures in the northwestern U.S. Also, above-average precipitation is favored across most of the northern tier of states (except the north-central U.S.) and in the Ohio and Tennessee Valleys, and drier-than-average conditions are more likely across the southern tier of the U.S. (see 3-month seasonal outlook released on 19 January 2012).

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 8 March 2012. 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.

Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
Camp Springs, MD 20746-4304

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Australia, Bureau of Meteorology.

La Niña shows some weakening

Issued on Tuesday 14 February | Product Code IDCKGEWWOO

The La Niña showed some signs of weakening over the past fortnight as the tropical Pacific Ocean warmed. However, La Niña remains in place and is likely to influence Australian climate over the coming months. Climate models surveyed by the Bureau show a continued decline of La Niña, with a neutral ENSO state expected in the southern hemisphere autumn.

Over the past fortnight, sea surface temperatures have warmed across the tropical Pacific, most significantly over the central to eastern Pacific regions, associated with a brief easing of the trade winds. Other indicators of La Niña, such as the Southern Oscillation Index (SOI), and cloudiness over the equatorial Pacific Ocean have generally remained steady at La Niña levels.

La Niña periods are usually, but not always, associated with above normal rainfall and below normal daytime temperatures from winter through summer across eastern and northern Australia. Tropical cyclone risk is increased for northern Australia during the cyclone season (November to April), peaking in February and March. For detailed rainfall, temperature and tropical cyclone outlooks, please see:www.bom.gov.au/climate/ahead.

Please Note: The ENSO Wrap Up will now be issued on Tuesdays.

Next update expected by 28 February 2012

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2009-12-07T17:50:00.003-07:00

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SST Anomaly

El nino/Lanina 2011/2012

La Niña shows some weakening

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