CPC and the contributors to the Forecast Forum caution potential users of
this predictive information that they can expect only modest skill.
Alert System Status: Not
conditions are expected to continue into the
Northern Hemisphere fall 2011.
June 2011, ENSO-neutral conditions continued as reflected by the overall pattern
of small sea surface temperature (SST) anomalies across the equatorial Pacific
Ocean (Fig. T18).
Other than Niño-1+2, all of the monthly Niño index values were near
average (Table T2). The
subsurface oceanic heat content anomaly (average temperature anomalies in the
upper 300m of the ocean) remained elevated, but weakened slightly throughout the
month, in accordance with the declining strength of above-average temperatures
at depth (Fig. T17). While
weak, the atmospheric circulation anomalies remained consistent with certain
aspects of La Niña. In particular,
convection continued to be enhanced over eastern Indonesia and suppressed over
the central equatorial Pacific, mainly south of the equator (Fig. T25).
Also, anomalous low-level easterly and upper-level westerly winds
persisted over the central Pacific (Figs. T20,
Collectively, these tropical Pacific anomalies indicate ENSO-neutral
conditions, but the atmospheric circulation continues to be characteristic of La
from a majority of the ENSO models, indicate ENSO-neutral will continue into the
Northern Hemisphere fall 2011 (three-month average in the Nino-3.4 index between
–0.5°C and +0.5°C; Figs.
over the last couple of weeks, forecasts created by the NCEP Climate Forecast
System (CFS) have begun to indicate the re-emergence of La Niña during Northern
Hemisphere fall 2011. Combined with the recent weakening of the positive
subsurface ocean anomalies and the lingering La Niña state of the atmosphere,
the possibility of a return to La Niña during the Northern Hemisphere fall 2011
has increased over the past month.
However, ENSO-neutral remains most likely into the Northern Hemisphere
fall 2011, with most models and all multi-model forecasts predicting ENSO-neutral
to continue through early 2012.
updates of oceanic and atmospheric conditions are available on the Climate
Niño/La Niña Current Conditions and Expert Discussions).