transition from La Niņa to ENSO-neutral conditions occurred during May 2011 as
sea surface temperatures were near-average across much of the equatorial Pacific
T18, Table T2).
The latest monthly Niņo indices were -0.5°C for the Niņo
3.4 region and +0.8°C for the Niņo
1+2 region (Table T2,
Consistent with these conditions, the oceanic thermocline (measured by
the depth of the 20°C
isotherm) remained slightly deeper than average over the eastern equatorial
Pacific (Figs. T15 and
T16), with sub-surface temperatures
above average in this region (Fig. T17).
the atmospheric circulation patterns during May continued to show some weak La
Niņa impacts. The equatorial
low-level easterly trade winds and upper-level westerly winds remained stronger
than average over the central equatorial Pacific (Table T1, Fig.
T20), while convection remained enhanced over
eastern Indonesia and suppressed across the central equatorial Pacific (Figs.
T25 and E3).
Collectively, these oceanic and atmospheric anomalies reflect a transition to
ENSO-neutral conditions but with weakening La Niņa impacts in the atmosphere.
the latest status of the ENSO cycle see the ENSO Diagnostic Discussion at: