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ENSO Forecast Discussion

ENSO and SST Model Forecasts

Canonical Correlation Model
Nino 3.4 Region: Historical  F1
Nino 3.4 Region: 0-4 Season  F2

NCEP Coupled Model
Eq. Pac. SST & Anomalies  F3
Nino 3 & Nino 3.4 Region  F4

NCEP Markov Model
Eq. Pac. SST & Anomalies  F5
Nino 3.4 Region  F6

LDEO Model
Eq. Pac. SST & Wind Stress Anoms  F7
Nino 3 Region  F8

Linear Inverse Modeling
Global Tropical SST Anomalies  F9
Nino 3.4 Region: Historical  F10

Scripps/MPI Hybrid Coupled Model
Eq. Pac. SST & Anomalies  F11

ENSO-CLIPER Model
All Nino Regions & SOI  F12

IRI Compilation of Forecasts
Nino3.4 Region  F13

Forecast Forum

AUGUST 2011

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 conditions have returned and are expected to gradually strengthen and continue into the Northern Hemisphere winter 2011-12.

Discussion:    

La Niña conditions returned in August 2011 due to the strengthening of negative sea surface temperature (SST) anomalies across the eastern half of the equatorial Pacific Ocean (Fig. T18).  With the exception of the far easternmost Niño-1+2 region, all of the monthly Niño index values were near –0.5°C or less (Table T2).  Also supporting the return of La Niña conditions was the strengthening of the below-average subsurface oceanic heat content anomaly (average temperature anomalies in the upper 300m of the ocean), in response to increased upwelling and further shoaling of the thermocline across the eastern Pacific Ocean (Fig. T17).  The atmospheric circulation over the tropical Pacific continued to exhibit La Niña characteristics, but remained weaker and less canonical than the wintertime atmospheric patterns.  For example, convection continued to be suppressed near the Date Line, but remained south of the equator, while convection was only weakly enhanced near Papua New Guinea (Fig. T25).  In addition, anomalous low-level easterly and upper-level westerly winds persisted over the central tropical Pacific (Figs. T20, T21).  Collectively, these oceanic and atmospheric patterns reflect the return of La Niña conditions. 

Over the last several months many models have predicted increasingly negative SST anomalies in the Nino-3.4 region during the upcoming Northern Hemisphere fall and winter. However, the majority of models continue to predict ENSO-neutral conditions for this period (Figs. F1-F13). The NCEP Climate Forecast System (CFS) has performed quite well over the past several months capturing the recent decrease in SST anomalies.  The better model performance, combined with the historical tendency for significant La Nina episodes (as in 2010-11) to be followed by relatively weaker La Niña episodes, leads to increased confidence that La Niña will persist into the winter.   While it is not yet clear what the ultimate strength of this La Niña will be, La Niña conditions have returned and are expected to gradually strengthen and continue into the Northern Hemisphere winter 2011-12.

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