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

MAY 2009

During May 2009, ENSO -neutral conditions persisted across the equatorial Pacific Ocean . However, sea surface temperature (SST) anomalies in the eastern equatorial Pacific Ocean continued to increase (Fig. T18).  The latest monthly SST index was +0.3°C in the Niño-3.4 region, and +0.6°C in the Niño-1+2 region (Table T2, Fig. T5).

The oceanic thermocline along the equator, measured by the depth of the 20°C isotherm, remained deeper than average across the equatorial Pacific Ocean during May (Figs. T15, T16). Consistent with these conditions, temperatures were 1^o-3^oC above average at thermocline depth across the equatorial Pacific (Fig. T17).

Although these oceanic anomalies reflected ENSO -neutral conditions, some lingering La Niña signals were still evident in the atmosphere. In particular, the patterns of 500-hPa height anomalies that have prevailed over both the North and South Pacific Oceans for the past several months were again evident in May. In the NH, this pattern featured below average heights over the central subtropical North Pacific and above average heights over the high latitudes of the central North Pacific (Fig. E9). In the SH, the pattern featured ongoing above average heights over the central South Pacific and below average heights over the high latitudes of the eastern South Pacific (Fig. E15).

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