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Climate Prediction Center

Climate Diagnostics Bulletin
Climate Diagnostics Bulletin - Home Climate Diagnostics Bulletin - Forecast Climate Diagnostics Bulletin - Extratropics


  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


Forecast Forum

La Niņa 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 Niņo indices were -0.6°C for the Niņo 3.4 region and 0.0°C for the Niņo 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 Niņa 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 Niņa conditions.

For the latest status of the ENSO cycle see the ENSO Diagnostic Discussion at:

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