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

Sea surface temperatures remained warmer than average across most of the equatorial Pacific Ocean during December (Fig. 1), although departures from average decreased in all of the Niño index regions during the month (Fig. 2). Equatorial ocean surface temperatures greater than +0.5°C (~1°F) above average were found between Indonesia and 170°W and in most of the eastern equatorial Pacific between 140°W and the South American coast. Departures greater than +1°C were found between 160°E and 180°W.

In spite of the slightly warmer-than-average oceanic temperatures, the monthly 850-hPa zonal wind indices, OLR index, 200-hPa zonal wind index, SOI and EQSOI do not indicate warm episode conditions. Over the past few months, these atmospheric indices have not shown any significant trends that would support either additional large-scale increases or any substantial decreases of SST anomalies in equatorial Pacific. However, many of these indices exhibited considerable week-to-week variability during late November and December in response to tropical intraseasonal (Madden-Julian Oscillation) activity. Wetter-than-average conditions, observed over the Indian Ocean in late November, shifted eastward to the western Pacific by late December. At the same time, the equatorial easterlies weakened over the western Pacific and westerlies developed near the date line (180°W) (Fig. 3). NOAA’s Climate Prediction Center will continue to monitor these features to determine what, if any, impacts this activity will have on surface and subsurface temperatures in the region between the date line and the South American coast.

A majority of the statistical and coupled model forecasts indicate near neutral conditions in the tropical Pacific (Niño 3.4 SST anomalies between -0.5°C and +0.5°C) through March 2004. Thereafter, the forecasts show increasing spread and greater uncertainty, during a time of the year when the skill level of all of the techniques is relatively low.

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 Niño/La Niña 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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Page last modified: July 10, 2003
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