Skip Navigation Links 
NOAA logo - Click to go to the NOAA home page National Weather Service   NWS logo - Click to go to the NWS home page
Climate Prediction Center

CPC Search
About Us
   Our Mission
   Who We Are

Contact Us
   CPC Information
   CPC Web Team

HOME > Expert Assessments > ENSO Diagnostic Discussion
issued by
February 5, 2004

Sea surface temperatures remained warmer than average in the central and western equatorial Pacific and near average in the eastern equatorial Pacific during January (Fig. 1). Equatorial ocean surface temperatures greater than +0.5°C (~1°F) above average were found between Indonesia and 165°W, and departures greater than +1°C were found between 160°E and 175°W. Since early December 2003, SST anomalies have decreased in all of the Niño regions (Fig. 2).

The monthly 850-hPa zonal wind indices, OLR index, 200-hPa zonal wind index, SOI and EQSOI have not shown any significant trends over the last few months that would support a transition to either El Niño or La Niña. However, many of these indices have exhibited considerable week-to-week variability since late November in response to tropical intraseasonal (Madden-Julian Oscillation) activity. Wetter-than-average conditions (enhanced convection), observed over the tropical Indian Ocean in late November, shifted eastward to the western Pacific by late December and into the central Pacific by early January. As the convective activity shifted eastward, the equatorial easterlies weakened over the western and central Pacific and westerlies developed near the date line (180°W) (Fig. 3). During the last half of January the equatorial easterlies intensified, becoming stronger than average over the central and western equatorial Pacific, as the convectively inactive phase of the MJO shifted eastward over the region. The recent period (the time that it takes for a particular phase of the oscillation to completely circle the Earth) of the MJO is between 45 and 50 days. During late January there were indications that the convectively active phase of the MJO was over the Indian Ocean. At the current rate of propagation, enhanced convection should shift into the western and central equatorial Pacific during February, accompanied by another period of weaker-than-average easterlies.

The weakening of the equatorial easterlies in late December 2003-early January 2004 initiated an eastward propagating oceanic Kelvin wave, which is evident in the recent evolution of upper ocean temperature anomalies (Fig. 4). More recent observations from the TAO buoy array indicate that this Kelvin wave is propagating eastward at about 8-10 degrees of longitude per week. At that rate, the Kelvin wave is expected to reach the vicinity of the west coast of South America around the end of February. NOAA’s Climate Prediction Center (CPC) will continue to monitor this situation to determine what, if any, impacts the Kelvin wave will have on surface and subsurface temperatures along 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.

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:

Climate Prediction Center
National Centers for Environmental Prediction
NOAA/National Weather Service
Camp Springs, MD 20746-4304

NOAA/ National Weather Service
National Centers for Environmental Prediction
Climate Prediction Center
5200 Auth Road
Camp Springs, Maryland 20746
Climate Prediction Center Web Team
Page last modified: July 10, 2003
Disclaimer Privacy Notice