Sea surface temperatures remained warmer than average
across most of the equatorial Pacific Ocean during December (Fig.
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
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
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
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.