Tropical Highlights – October 2011

 

 

La Niña conditions strengthened during October 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 -0.6°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 and T16), where corresponding sub-surface temperatures were 1-5°C below average (Fig. T17).

Also in October, the equatorial low-level easterly trade winds and upper-level westerly winds were stronger than average over the western equatorial Pacific (Table T1, Figs. T20 and T21).  Convection remained suppressed near the Date Line (Figs. T25 and E3) but was near-average over Indonesia, which reflected the effect of the intraseasonal oscillation seen in October (Fig. T12). Collectively, these oceanic and atmospheric anomalies reflect a strengthening 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