Surface and subsurface temperatures remained warmer than
average across most of the equatorial Pacific Ocean during November (Fig. 1
and Fig. 2, respectively). Equatorial ocean surface temperatures greater than
+0.5°C (~1°F) above average were found in most areas
between Indonesia and the South American coast.
Departures greater than +1°C
were found between 150°E
and 170°W. Positive SST anomalies were observed in all four Niņo
index regions for the second consecutive month (Fig. 3). However, the 850-hPa zonal wind indices, OLR
index, 200-hPa zonal wind index, SOI and EQSOI all indicate ENSO-neutral
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 the
A majority of the statistical and coupled model forecasts indicate
near-average conditions in the tropical Pacific (Niņo
3.4 SST anomalies between -0.5°C
through Northern Hemisphere winter 2003-2004. However, some forecasts
indicate that weak warm episode conditions will develop during the winter,
which is consistent with observed trends in SST anomalies, particularly in
the vicinity of the date line.
The three-month (September-November) average SST anomaly in the Niņo
3.4 region (+0.4°C)
is just below the threshold (+0.5°C)
required for NOAA to declare a weak Pacific warm episode (El Niņo).
It is likely that the October-December 2003 average will reach that
threshold and that borderline weak El Niņo
/ ENSO-neutral conditions will persist through the Northern Hemisphere
winter of 2003-04. However, it seems unlikely that classical El Niņo
conditions will develop along the west coast of South America.
In the past, weak Pacific warm episodes have not shown consistent
temperature and precipitation impacts, especially for areas outside the
tropical Pacific. Therefore, these conditions are not likely to have
significant impacts on the wintertime temperature and precipitation patterns
over the United States.