A transition from
La Niņa to
-neutral conditions was observed
during April 2009, as negative sea
surface temperature (SST) anomalies further weakened across the equatorial
and positive anomalies developed in
areas of the eastern Pacific (Fig.
The latest monthly SST index was -0.2°C in the Niņo-3.4 region, and 0.0°C
in the Niņo-4 region (Table T2,
The oceanic thermocline along
the equator, measured by the depth of the 20°C
isotherm, remained deeper than average across the Pacific and shallower than
average in the far eastern Pacific during April (Figs. T15,
T16). Consistent with these conditions,
temperatures were 1-3oC above average at thermocline depth across the
equatorial Pacific (Fig. T17). Convection
remained suppressed over the central equatorial
and enhanced in the western Pacific (Figs.
T25 and E3).
Collectively, this combination of oceanic and atmospheric conditions reflects a
transition from weak La Niņa to
the latest status of the ENSO cycle see the ENSO Diagnostic Discussion at: