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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

APRIL 2009

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: Final La Niña Advisory      

Outlook:  

            ENSO-neutral conditions are expected to continue into the Northern Hemispheric Summer.

Discussion:    

During April 2009, the equatorial Pacific Ocean transitioned from La Niña to ENSO -neutral conditions, ending the 2008-09 La Niña.  Negative sea surface temperature (SST) anomalies weakened across the equatorial Pacific Ocean and positive anomalies developed in areas of the eastern Pacific (Fig. T18) .  Correspondingly, the monthly SST indices were near zero in all Niño regions, except for the easternmost Niño-1+2 region (Table T2).  Subsurface oceanic heat content anomalies (average temperatures in the upper 300m of the ocean) became positive for the first time since mid-August 2008, reflecting an eastward spread of above-average temperatures near thermocline depth (Fig. T17). 

Atmospheric anomalies consistent with La Niña weakened during April, with enhanced convection decreasing over Indonesia , although convection remained suppressed near the International Date Line (Fig. T25).  Also, Madden Julian Oscillation (MJO) activity strongly influenced the atmospheric circulation across the global tropics, and contributed to the periodic fluctuation in the strength of the low-level easterly winds and upper-level westerly winds over the equatorial Pacific Ocean (Figs. T20 and T21 ).  Collectively, these oceanic and atmospheric anomalies are consistent with a transition to ENSO-neutral conditions.

A majority of model forecasts for the Niño-3.4 region show that ENSO-neutral conditions will continue through the remainder of 2009 (Figs. F1-F13).   The dynamical models, such as the NCEP Climate Forecast System (CFS), increasingly favor above-average temperatures in the Niño-3.4 region, while statistical models predict below- or near-average temperatures.  Compared to the statistical models, the dynamical models are more responsive to subsurface temperatures, which have recently increased as positive anomalies have spread eastward.  Based on current observations, recent trends, and model forecasts, ENSO-neutral conditions are expected to continue into the Northern Hemisphere Summer.

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