The canonical correlation analysis (CCA) forecast of
SST in the central Pacific (Barnett et al. 1988, Science, 241,
192‑196; Barnston and Ropelewski
1992, J. Climate, 5, 1316‑1345), is shown in Figs. F1 and F2. This forecast is produced routinely by the
Prediction Branch of the Climate Prediction Center. The
predictions from the National Centers for Environmental Prediction (NCEP)
Coupled Forecast System Model (CFS03) are presented in Figs. F3 and
F4a, F4b. Predictions from the
Markov model (Xue, et al. 2000: J. Climate, 13,
849‑871) are shown in Figs. F5 and F6. Predictions from the latest version of the
LDEO model (Chen et al. 2000: Geophys. Res.
Let., 27, 2585‑2587) are shown in Figs. F7
and F8. Predictions using linear inverse modeling (Penland and Magorian 1993: J.
Climate, 6, 1067‑1076) are shown in Figs. F9 and F10. Predictions from the Scripps / Max Planck
Institute (MPI) hybrid coupled model (Barnett et al. 1993: J. Climate, 6,
1545‑1566) are shown in Fig. F11.
Predictions from the ENSO‑CLIPER statistical model (Knaff and Landsea 1997, Wea.
Forecasting, 12, 633‑652) are shown in Fig. F12. Niño 3.4 predictions are summarized in Fig.
F13, provided by the Forecasting and Prediction Research Group of the IRI.
The CPC and the contributors to the Forecast Forum caution
potential users of this predictive information that they can expect only modest
ENSO Alert System Status: La Niña Watch
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. T18).
The weekly Niño indices were volatile during the month (Table T2), with negative values weakening to near zero late in the month in
the Niño-4, Niño-3.4, and Niño-3 regions.
In contrast, sub-surface temperature anomalies were increasingly
negative during September, reflecting the shallow depth of the thermocline
across the central and eastern Pacific (Fig. T17). Also, convection was suppressed near the
International Date Line and enhanced near Indonesia (Fig. T25). Over the western
equatorial Pacific Ocean, low-level trade winds were anomalously easterly and
upper-level winds were anomalously westerly (Fig. T20, Fig. T21). 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 and North American Multi-Model Ensemble (NMME) (Figs. F1-F13).
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.
updates of oceanic and atmospheric conditions are available on the Climate
Prediction Center homepage (El
Niño/La Niña Current Conditions and Expert Discussions).