ENSO
Alert System Status: La Niña Watch
Synopsis: La Niña conditions are favored
(~55-65%) during the Northern Hemisphere fall and winter 2017-18.
During September, ENSO-neutral conditions were
reflected in near-to-below average sea surface temperatures (SSTs) across most
of the central and eastern Pacific Ocean (Fig. 1). The weekly Niño indices were volatile during
the month, with negative values increasing to near zero during the past week in
the Niño-4, Niño-3.4, and Niño-3 regions (Fig. 2). In contrast, sub-surface temperature
anomalies were increasingly negative during September (Fig. 3), reflecting the shallow
depth of the thermocline across the central and eastern Pacific (Fig. 4). Also, convection was suppressed near the
International Date Line and enhanced near Indonesia (Fig. 5). Over the western equatorial Pacific Ocean,
low-level trade winds were anomalously easterly and upper-level winds were
anomalously westerly. Overall, the ocean
and atmosphere system remains consistent with ENSO-neutral, although edging
closer to La Niña conditions.
For the upcoming Northern Hemisphere fall and winter
2017-18, a weak La Niña is favored in the dynamical model averages of the
IRI/CPC plume (Fig. 6) and North American Multi-Model Ensemble (NMME) (Fig.
7). Several models indicate a period of
near-average Niño-3.4 values in the upcoming weeks, but then predict
reinvigorated growth of negative SST anomalies across the equatorial Pacific
Ocean. These forecasts are supported by
the ongoing easterly wind anomalies across portions of the Pacific Ocean and the
reservoir of below-average subsurface temperatures. In summary, La Niña conditions are favored (~55-65%) during the Northern Hemisphere
fall and winter 2017-18 (click CPC/IRI consensus forecast for the chance of each outcome for
each 3-month period).
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 are also updated monthly in the Forecast Forum of CPC's Climate Diagnostics
Bulletin. Additional perspectives and analysis are also available in an ENSO blog. The next ENSO Diagnostics Discussion is scheduled
for 9 November 2017. 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@noaa.gov.
Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
College Park, MD 20740
National Centers for Environmental Prediction
NOAA/National Weather Service
College Park, MD 20740
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