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 Advisory

 

Outlook:

 

A transition from La Niña to ENSO-Neutral is likely in the next month or so, with an 80% chance of ENSO-neutral during May-July 2021. 

 

Discussion:  

 

La Niña continued during March, reflected by negative sea surface temperatures (SST) anomalies, which extended across much of the equatorial Pacific Ocean (Fig. T18). Except for Niño-1+2, the monthly Niño index values were at or near -0.5ºC (Table T2).  Sub-surface ocean temperatures also weakened during the month, with the integrated anomalies averaged between the 180-100°W becoming positive during the middle of the month. Currently, negative subsurface temperature anomalies are present from the surface to approximately ~100m below the surface only in the eastern Pacific between 110°W and 80°W (Fig. T17).  Low-level easterly wind anomalies are present but weak across the equatorial Pacific, and are most notable in the far western Pacific (Fig. T20). Upper-level wind anomalies were westerly across most of the tropical Pacific (Fig. T21).  The suppression of tropical convection over the western and central Pacific persisted during March, although the enhancement of rainfall around the Philippines and Indonesia weakened (Fig. T25). The Southern Oscillation and Equatorial Southern Oscillation indices were weakly positive in March (Table T1 & Fig. T2).  Overall, the trend in the coupled ocean-atmosphere system is consistent with a weakening La Niña.

Most of the models in the IRI/CPC plume predict a transition to ENSO-neutral during the Northern Hemisphere spring 2021 (Figs. F1-F12).  The forecaster consensus agrees that a transition is imminent, with a 50-50% chance of La Niña or ENSO-neutral for the March-May average, and then predicts ENSO-neutral to continue at least through the Northern Hemisphere summer.  In part, due to the uncertainty in predictions made at this time of year, the forecast for the Northern Hemisphere Fall 2021 has lower confidence with a 40-50% chance of either La Niña or ENSO-Neutral, with a small chance for El Niño.  In summary, a transition from La Niña to ENSO-Neutral is likely in the next month or so, with an 80% chance of ENSO-neutral during May-July 2021.

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