During May 2009,
conditions persisted across the equatorial
However, sea surface temperature (SST) anomalies in the eastern equatorial
continued to increase (Fig. T18).
The latest monthly SST index was +0.3°C in the Niņo-3.4 region, and
+0.6°C in the Niņo-1+2 region (Table T2,
The oceanic thermocline along
the equator, measured by the depth of the 20°C
isotherm, remained deeper than average across the equatorial
during May (Figs. T15, T16).
Consistent with these conditions, temperatures were 1o-3oC
above average at thermocline depth across the equatorial Pacific (Fig. T17).
Although these oceanic anomalies
conditions, some lingering La Niņa signals were still evident in the
atmosphere. In particular, the patterns of 500-hPa height anomalies that have
prevailed over both the North and
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.
the latest status of the ENSO cycle see the ENSO Diagnostic Discussion at: