Tropical Highlights

  Table of Atmospheric Indices  (Table 1)

  Table of Oceanic Indices  (Table 2)

  Time Series

  Time-Longitude Sections

  Mean & Anomaly Fields

  Appendix 1: Outside Contributions

Tropical Highlights

AUGUST 2011

La Niña conditions developed during August 2011 as sea surface temperatures were below-average across much of the eastern equatorial Pacific Ocean (Fig. T18, Table T2). The latest monthly Niño indices were -0.6°C for the Niño 3.4 region and 0.0°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) was shallower than average in the east-central equatorial Pacific (Figs. T15 and T16). The corresponding sub-surface temperatures were 1-3°C below average in the east-central equatorial Pacific (Fig. T17).

The atmospheric circulation patterns during August continued to show some weak La Niña impacts.  The equatorial low-level easterly trade winds and upper-level westerly winds remained stronger than average over the central equatorial Pacific (Table T1, Figs. T20 and T21), while convection remained enhanced over western equatorial Pacific and suppressed near the Date Line and south of the Equator (Figs. T25 and E3). Collectively, these oceanic and atmospheric anomalies reflect the return 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