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HOME > Expert Assessments > ENSO Diagnostic Discussion
issued by
April 8, 2004

Sea surface temperature (SST) anomalies were near zero in all of the Niņo regions during March 2004 (Fig. 1). By the end of the month, near-average or slightly cooler-than-average SSTs were observed everywhere east of 150°W, with positive anomalies greater than +0.5°C (~1°F) being restricted to portions of the region between Indonesia and 175°W (Fig. 2). Subsurface temperature anomalies in mid-March were generally positive in the western and central equatorial Pacific and negative in the eastern equatorial Pacific (Fig. 3). This represents a steeper-than-average thermocline slope, which is consistent with the stronger-than-average easterly winds over the central equatorial Pacific during the last three months (Fig. 4).

The 850-hPa zonal wind indices, OLR index, 200-hPa zonal wind index, SOI and EQSOI have exhibited considerable intraseasonal variability since late November in association with tropical Madden-Julian Oscillation (MJO) activity. In spite of that variability, certain average atmospheric patterns have become apparent since November. These include: 1) stronger-than-average easterly winds between 160E and 150W (Fig. 4, top panel), and 2) weaker-than-average convection (drier-than-average conditions) over the central equatorial Pacific (Fig. 4, bottom panel). These conditions are consistent with the observed decrease in SST anomalies in the central equatorial Pacific that occurred from December 2003 through March 2004.

A majority of the statistical and coupled model forecasts indicate near neutral conditions in the tropical Pacific (Niņo 3.4 SST anomalies between -0.5°C and +0.5°C) through the northern summer 2004 Thereafter, the forecasts show increasing spread and greater uncertainty. Given the recent trends and observed oceanic and atmospheric patterns discussed above, it is likely that ENSO-neutral conditions will continue for the next 3-6 months.

This discussion is a consolidated effort of NOAA and its funded institutions. Weekly updates for SST, 850-hPa wind, OLR and features of the equatorial subsurface thermal structure are available on the Climate Prediction Center web page at (Weekly Update). Forecasts for the evolution of El Niņo/La Niņa are updated monthly in the Forecast Forum section of CPC's Climate Diagnostics Bulletin. To receive an e-mail notification when the monthly ENSO Diagnostic Discussions are released, please send your e-mail address to:

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