August 2007, negative equatorial sea surface temperature (SST) anomalies in the
eastern equatorial Pacific expanded westward, and now extend from the coast of
South America to the date line (180ºW)
(Fig. T18). This pattern is reflected in
negative values of the Niño 1+2 (-1.6), Niño 3 (-1.1), and Niño 3.4 (-0.5)
region SST indices (Table
T2). The equatorial oceanic thermocline
during August, measured by the depth of the 20ºC
isotherm, featured a continuation of below-average depths over the eastern
equatorial Pacific and near-average depths across the western and central
equatorial Pacific (Figs.
T15, T16). As a
result, temperatures in the eastern equatorial Pacific remained generally 1-3ºC
below average at thermocline depth (Fig.
August 2007, low-level easterly anomalies (more than
3.0 m s-1) were observed over the
central equatorial Pacific (Fig.
T20). This anomaly pattern has persisted since February (Fig.
T13), and is consistent with the shallower-than-average thermocline and
cooler SSTs farther east. This wind pattern was also
associated with enhanced convection (above-average rainfall amounts) across
, and a continuation of suppressed convection
(below-average rainfall amounts) across the central and eastern equatorial
Pacific (Figs. T26,
E3). Consistent with these
anomalies, the equatorial SOI remained positive (+1.2) (Fig.
T2), although the
– Darwin SOI was near-average (+0.1) (Table
T1, Fig. T1). This overall combination of
oceanic and atmospheric conditions reflects the development of La Niña
For the latest status of the ENSO cycle see the ENSO Diagnostic Discussion at: