Tropical Highlights – December 2011

 

 

La Niña conditions continued during December 2011 as sea surface temperature anomalies were well below -0.5°C across the eastern and central equatorial Pacific Ocean (Fig. T18, Table T2). The latest monthly Niño indices were -1.0°C for the Niño 3.4 region and -1.1°C for the Niño 1+2 region (Table T2, Fig. T5). Consistent with these conditions, the oceanic thermocline (measured by the depth of the 20°C isotherm) remained shallower than average in the east-central equatorial Pacific (Figs. T15, T16), where corresponding sub-surface temperatures were 1-4°C below average (Fig. T17).

Also in December, the equatorial low-level easterly trade winds and upper-level westerly winds were stronger than average over the western and central equatorial Pacific (Table T1, Figs. T20, T21).  Convection remained suppressed in the western and central equatorial Pacific and enhanced across Indonesia and northern Australia (Figs. T25, E3). Collectively, these oceanic and atmospheric anomalies reflect a continuation of La Niña conditions.

 

 

For the latest status of the ENSO cycle see the ENSO Diagnostic Discussion at: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html