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

FEBRUARY 2011

La Niña weakened during February 2011 as the magnitude of the negative sea surface temperature anomalies decreased across much of the equatorial Pacific Ocean (Fig. T18, Table T2). The latest monthly Niño indices were -1.3°C for the Niño 3.4 region and +0.1°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 slightly shallower than average over the eastern equatorial Pacific (Figs. T15 and T16), with sub-surface temperatures reaching 1°C to 4°C below average in this region (Fig. T17).

Also during February, the equatorial low-level easterly trade winds remained stronger than average over the western and central Pacific (Table T1, Fig. T20), while convection remained enhanced over Indonesia and suppressed across the western and central equatorial Pacific (Figs. T25 and E3). Also, over the eastern Pacific the low-level cross-equatorial flow and the associated upwelling were notably weaker during February. Collectively, these oceanic and atmospheric anomalies reflect a weakening La Niña.

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