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HOME > Expert Assessments > ENSO Diagnostic Discussion
issued by
August 7, 2003

Current atmospheric and oceanic conditions in the tropical Pacific are near average and do not support the development of either La Niņa or El Niņo in the next few months. Equatorial sea-surface temperature anomalies greater than +0.5°C persisted in the region west of the date line, while negative anomalies remained in the eastern Pacific, near the South American coast (Fig. 1). During July very little net change was observed in the SST anomalies in the Niņo regions (Fig. 2).

Since late May positive equatorial upper-ocean temperature departures have spread eastward into the central and eastern Pacific (see Fig. 3 for evolution during July 2003). This evolving subsurface pattern is associated with an eastward propagating oceanic Kelvin wave, resulting from a period of weaker-than-average easterlies in the central equatorial Pacific that occurred during late May and early June. SST anomalies in the Niņo 3.4 and Niņo 3 regions (Fig. 2) increased during early-June through early July, but then decreased during the last half of July, as the equatorial easterlies strengthened.

Some atmospheric indices, such as the Tahiti-Darwin SOI, and central equatorial Pacific low-level (850-hPa) zonal wind and OLR, have displayed considerable month-to-month variability since May 2003 and no consistent trend towards either La Niņa or El Niņo.

A majority of the statistical and coupled model forecasts indicate near neutral conditions (Niņo 3.4 SST anomalies between -0.5°C and +0.5°C) for the remainder of 2003 and early 2004. This is consistent with current conditions and the lack of any consistent trends in the suite of oceanic and atmospheric indices.

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 temperature 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 CPC's Climate Diagnostics Bulletin Forecast Forum. 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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