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 ENSO‑CLIPER
statistical model (Knaff and Landsea 1997, Wea. Forecasting, 12, 633‑652)
are shown in Fig. F11. Niño 3.4
predictions are summarized in Fig. F12, 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 Advisory
Outlook:
La
Niña is likely to continue through the Northern Hemisphere winter 2020-21 (~95%
chance during January-March) and into spring 2021 (~65% chance during
March-May).
Discussion:
La
Niña strengthened during October, as indicated by well below-average sea
surface temperatures (SSTs) extending from the Date Line to the eastern Pacific
Ocean (Fig. T18).
Most Niño regions cooled further from last month, and the Niño-3.4 index
was -1.4ºC in October (Table T2). The equatorial subsurface
temperature anomalies (averaged from 180°-100°W) also became colder, and
continue to reflect below-average temperatures from the surface to 200m depth
in the eastern Pacific Ocean (Fig. T17).
The atmospheric circulation anomalies over the tropical Pacific Ocean
remained consistent with La Niña.
Low-level wind anomalies were easterly across most of the tropical
Pacific and strengthened during October (Fig.
T20). Upper-level westerly wind
anomalies expanded over most of the tropical Pacific (Fig. T21). Tropical
convection continued to be suppressed from the western Pacific to the Date
Line, and enhanced convection remained over Indonesia (Fig. T25). Also, both the Southern Oscillation and
Equatorial Southern Oscillation indices were positive (Table T1 & Fig. T2).
Overall, the coupled ocean-atmosphere system indicates the continuation
of La Niña.
A
majority of the models in the IRI/CPC plume predict La Niña (Niño-3.4 index
less than -0.5°C) to persist through the Northern Hemisphere winter 2020-21 and
to weaken during the spring (Figs.
F1-F12). The latest forecasts from several
models suggest the possibility of a strong La Niña (Niño-3.4 index values at
-1.5ºC) during the peak November-January season. The forecaster consensus supports that view
in light of significant atmosphere-ocean coupling already in place. In summary, La Niña is likely to continue through the Northern Hemisphere winter
2020-21 (~95% chance for January-March) and spring 2021 (~65% chance for March-May).
Weekly
updates of oceanic and atmospheric conditions are available on the Climate
Prediction Center homepage (El
Niño/La Niña Current Conditions and Expert Discussions).