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

DECEMBER 2008

Negative sea surface temperature (SST) anomalies strengthened across the central and east-central equatorial Pacific Ocean during December 2008 (Fig. T18).  The latest monthly SST index was -0.7°C in the Niño-3.4 region, and -0.6°C in the Niño-4 region (Table T2).

The oceanic thermocline along the equator, measured by the depth of the 20°C isotherm, featured shallower-than-average depths across the eastern equatorial Pacific during December (Figs. T15, T16). Consistent with this pattern, subsurface temperatures in the region were 1-5^oC below average at thermocline depth (Fig. T17).

Enhanced low-level easterly winds and upper-level westerly winds were present across the equatorial Pacific Ocean during December (Figs. T20, T21). These conditions continued to be associated with suppressed convection over the central equatorial Pacific Ocean and enhanced convection across Indonesia (Fig. T25). This combination of conditions suggests that La Niña is developing.

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