Forecast Forum
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
skill.
ENSO Alert System Status: La Niña Watch
Outlook:
There is an increasing chance (~55-60%) of La Niña during the Northern
Hemisphere fall and winter 2017-18.
Discussion:
Over the last month, equatorial sea surface
temperatures (SSTs) were near-to-below average across the central and eastern
Pacific Ocean (Fig. T18).
ENSO-neutral conditions were apparent with the monthly Niño-3.4 SST
index value of -0.2°C (Table T2).
While temperature anomalies were variable at the surface, they became
increasingly negative in the sub-surface ocean, due to the shoaling of the
thermocline across the east-central and eastern Pacific (Fig. T17). Though
remaining mostly north of the equator, convection was suppressed over the
western and central Pacific Ocean and slightly enhanced near Indonesia (Fig. T25). The
low-level trade winds were stronger than average over a small region of the far
western tropical Pacific Ocean, and upper-level winds were anomalously easterly
over a small area of the east-central Pacific (Fig. T20, Fig. T21). Overall, the
ocean and atmosphere system remains consistent with ENSO-neutral.
A majority of the models in the IRI/CPC suite of
Niño-3.4 predictions favor ENSO-neutral through the Northern Hemisphere 2017-18
winter (Figs. F1-F13). However, the
most recent predictions from the NCEP Climate Forecast System (CFSv2) and the
North American Multi-Model Ensemble (NMME) indicate the formation of La Niña as
soon as the Northern Hemisphere fall 2017.
Forecasters favor these predictions in part because of the recent
cooling of surface and sub-surface temperature anomalies, and also because of
the higher degree of forecast skill at this time of year. In summary, there is an increasing chance (~55-60%) of La Niña during the Northern
Hemisphere fall and winter 2017-18.
Weekly
updates of oceanic and atmospheric conditions are available on the Climate
Prediction Center homepage (El
Niño/La Niña Current Conditions and Expert Discussions).