[Vision2020] 9 June 2011: ENSO Alert System Status: Final La Niña Advisory

[Ted Moffett]

La Niña Impacts in the Pacific Northwest
http://www.ccb.ucar.edu/lanina/report/mantua.html
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http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html

EL NIÑO/SOUTHERN OSCILLATION (ENSO)
DIAGNOSTIC DISCUSSION
issued by
CLIMATE PREDICTION CENTER/NCEP
9 June 2011

ENSO Alert System Status: Final La Niña Advisory

Synopsis: ENSO-neutral conditions have developed and are expected to
continue at least through the Northern Hemisphere summer 2011.

A transition from La Niña to ENSO-neutral conditions occurred during
May 2011 as indicated by generally small sea surface temperature (SST)
anomalies across the equatorial Pacific Ocean east of the Date Line
(Fig. 1). The latest weekly Niño index values (Fig. 2) showed
near-average SSTs in the central and east-central equatorial Pacific
(Niño-4 index of –0.2oC and Niño 3.4 index of –0.1oC), and
above-average SSTs in the eastern equatorial Pacific (Niño-1+2 index
of +0.7oC). The subsurface oceanic heat content anomalies (average
temperatures in the upper 300m of the ocean, Fig. 3) remained
elevated, but relatively constant during the month, reflecting a large
area of above-average temperatures at depth (Fig. 4). Consistent with
other transitions to ENSO-neutral conditions, the atmospheric
circulation anomalies continued to show some features consistent with
La Niña, albeit at weaker strength. Convection was enhanced over
eastern Indonesia and suppressed over the central equatorial Pacific
(Fig. 5). Also, anomalous low-level easterly and upper-level westerly
winds weakened but persisted over the central Pacific. Collectively,
these oceanic and atmospheric anomalies reflect a transition to
ENSO-neutral conditions, but with lingering La Niña-like atmospheric
impacts, particularly in the global Tropics.

Current observed trends, along with forecasts from a majority of the
ENSO models, indicate ENSO-neutral will continue through the Northern
Hemisphere summer 2011 (three-month average in the Niño-3.4 index
between –0.5oC and +0.5oC; Fig. 6). Thereafter, most models and all
multi-model forecasts (shown by the thick lines) predict ENSO-neutral
to continue through the remainder of 2011. However, the status of ENSO
beyond the Northern Hemisphere summer remains more uncertain due to
lower model forecast skill at longer lead times, particularly during
this time of year.

This discussion is a consolidated effort of the National Oceanic and
Atmospheric Administration (NOAA), NOAA's National Weather Service,
and their funded institutions. Oceanic and atmospheric conditions are
updated weekly on the Climate Prediction Center web site (El Niño/La
Niña Current Conditions and Expert Discussions). Forecasts for the
evolution of El Niño/La Niña are updated monthly in the Forecast Forum
section of CPC's Climate Diagnostics Bulletin. The next ENSO
Diagnostics Discussion is scheduled for 7 July 2011. To receive an
e-mail notification when the monthly ENSO Diagnostic Discussions are
released, please send an e-mail message to:
ncep.list.enso-update at noaa.gov.

Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
Camp Springs, MD 20746-4304
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Vision2020 Post: Ted Moffett