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: El Niño Watch

 

Outlook:

 

A transition from ENSO-neutral is expected in the next couple of months, with a greater than 90% chance of El Niño persisting into the Northern Hemisphere winter.

 

Discussion:  

 

During April, above-average sea surface temperatures (SSTs) expanded slightly westward to the east-central equatorial Pacific Ocean (Fig. T18).  The monthly Niño-3.4 index value was +0.2C, with the easternmost Niño-3 and Niño1+2 regions at +0.4C and +2.5C, respectively (Table T2).  Area-averaged subsurface temperatures anomalies continued to increase, reflecting widespread positive temperature anomalies below the surface of the equatorial Pacific Ocean (Fig. T17).  Low-level wind anomalies were westerly during mid-April before switching back to easterly by the end of the month (Fig. T20).  Upper-level wind anomalies were westerly across most of the Pacific Ocean (Fig. T21).  Suppressed convection was observed over parts of Indonesia and anomalies weakened near the Date Line (Fig. T25). While the warming near coastal South America remains striking, the basin-wide coupled ocean-atmosphere system remained consistent with ENSO-neutral.

The most recent IRI plume also indicates El Niño is likely to form during the May-July season and persist into the winter (Figs. F1-F12).  The combination of a forecasted third westerly wind event in mid-late May, and high levels of above-average oceanic heat content, means that a potentially significant El Niño is on the horizon.  While at least a weak El Niño is likely, the range of possibilities at the end of the year (November-January) include a 80% chance of at least a moderate El Niño (Niño-3.4 >= 1.0C) to a ~55% chance of a strong El Niño (Niño-3.4 >= 1.5C).  It is still possible the tropical atmosphere does not couple with the ocean, and El Niño fails to materialize (5-10% chance).  In summary, a transition from ENSO-neutral is expected in the next couple of months, with a greater than 90% chance of El Niño persisting into the Northern Hemisphere winter.

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