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 (CFSv2) 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 from the ENSO‑CLIPER statistical model (Knaff and Landsea 1997, Wea. Forecasting, 12, 633‑652) are shown in Fig. F9.  Niño 3.4 predictions are summarized in Fig. F10, 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:

 

ENSO-neutral is favored for the remainder of summer (~60% chance in the July-September season), with La Niña possibly emerging during the August-October season and lasting through the 2021-22 winter (~70% chance during November-January).

 

Discussion:

 

Recently, sea surface temperatures (SSTs) were near-to-below average in the central and east-central equatorial Pacific, with above-average SSTs in the far eastern Pacific (Fig. T18).  For the month, most Niño indices were slightly negative (-0.1ºC to -0.3ºC) except for the Niño-1+2 index, which was +0.6ºC (Table T2).  Subsurface temperatures cooled considerably in July, becoming quite negative (averaged from 180-100ºW), reflecting the emergence of below-average subsurface temperatures east of the Date Line (Fig. T17).  Low-level wind anomalies were easterly over the east-central Pacific Ocean, while upper-level wind anomalies were westerly across the eastern Pacific (Fig. T20 & T21).  Tropical convection was suppressed over the western Pacific Ocean and enhanced over a small region near Indonesia (Fig. T25).  Given the surface conditions, the ocean-atmosphere system reflected ENSO-neutral.

Compared to last month, forecasts from the IRI/CPC plume are generally cooler in the Niño-3.4 SST region during the fall and winter 2021-22 (Figs. F1-F10).  Recent model runs from the NCEP CFSv2 and the North American Multi-Model Ensemble suggest the onset of a weak La Niña in the coming months, persisting through winter 2021-22.  The forecaster consensus continues to favor these models, which is also supported by the noticeable decrease in the observed subsurface temperature anomalies this past month.  In summary, ENSO-neutral is favored for the remainder of summer (~60% chance in the July-September season), with La Niña possibly emerging during the August-October season and lasting through the 2021-22 winter (~70% chance during November-January).

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