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 (~85% chance) and into spring 2021 (~60% chance during February-April).

 

Discussion:  

 

La Niña continued during September, as evidenced by below-average sea surface temperatures (SSTs) extending from the Date Line to the eastern Pacific Ocean (Fig. T18).  The SST indices in the two westernmost Niño regions, Niño-4 and Niño-3.4, cooled this month, and the Niño-3.4 index was -1.0ºC (Table T2).  The equatorial subsurface temperature anomalies (averaged from 180°-100°W) remained substantially unchanged, and continued 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 upper-level wind anomalies were westerly over the east-central Pacific (Figs. T20 & T21). Tropical convection continued to be suppressed from the western Pacific to the Date Line, and a slight enhancement of convection emerged over Indonesia (Fig. T25).  Also, both the Southern Oscillation and Equatorial Southern Oscillation indices remained 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, including the NCEP CFSv2, suggest the likelihood of a moderate or even strong La Niña (Niño-3.4 index values < -1.0ºC) 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 (~85% chance) and into spring 2021 (~60% chance during February-April).

Weekly updates of oceanic and atmospheric conditions are available on the Climate Prediction Center homepage (El Niño/La Niña Current Conditions and Expert Discussions).