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 Watch

 

Outlook:

 

There is a ~60% chance of La Niña development during Northern Hemisphere fall 2020 and continuing through winter 2020-21 (~55% chance).

 

Discussion:  

 

By early August 2020, sea surface temperatures (SSTs) were below average in the equatorial Pacific from the Date Line to the west coast of South America (Fig. T18).  The monthly Niño-3.4 and Niño-3 indices were at -0.3ºC and -0.5ºC, respectively (Table T2).  Negative equatorial subsurface temperature anomalies (averaged across 180°-100°W), which had weakened during June and early July, began re-strengthening in mid-July as below-average subsurface temperatures re-emerged in the east-central equatorial Pacific (Fig. T17).  During July, low-level wind anomalies were easterly across most of the equatorial Pacific (Fig. T20), while upper-level wind anomalies were westerly over portions of the far western, central, and eastern Pacific (Fig. T21).  Tropical convection was suppressed over the western and central Pacific, and was near average over Indonesia (Fig. T25). Overall, the combined oceanic and atmospheric system remained consistent with ENSO-neutral.

The models in the IRI/CPC plume (Figs. F1-F12) are split between La Niña and ENSO-neutral (Niño-3.4 index between -0.5°C and +0.5°C) during the fall and winter, but slightly favor La Niña from the August-October through the November-January seasons. Based largely on dynamical model guidance, the forecaster consensus favors La Niña development during the August-October season, lasting through winter 2020-21. In summary, there is a ~60% chance of La Niña development during Northern Hemisphere fall 2020 and continuing through winter 2020-21 (~55% chance). 

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