Tropical Highlights � December 2011

 

 

La Ni�a 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 Ni�o indices were -1.0�C for the Ni�o 3.4 region and -1.1�C for the Ni�o 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 Ni�a 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