Sea surface temperature (SST) anomalies
were near zero in all of the Niņo
regions during March 2004 (Fig. 1). By the end of the month, near-average or slightly
cooler-than-average SSTs were observed everywhere east of 150°W,
with positive anomalies greater than +0.5°C
(~1°F) being
restricted to portions of the region between
Indonesia and 175°W (Fig. 2). Subsurface temperature anomalies in mid-March were generally
positive in the western and central equatorial Pacific and negative in the
eastern equatorial Pacific (Fig. 3). This represents a steeper-than-average
thermocline slope, which is consistent with the stronger-than-average
easterly winds over the central equatorial Pacific during the last three
months (Fig. 4).
The 850-hPa zonal wind indices, OLR index, 200-hPa zonal wind
index, SOI and EQSOI have exhibited considerable intraseasonal variability
since late November in association with tropical Madden-Julian Oscillation (MJO)
activity. In spite of that variability, certain average atmospheric patterns
have become apparent since November. These include: 1) stronger-than-average
easterly winds between 160E and 150W (Fig. 4, top panel), and 2)
weaker-than-average convection (drier-than-average conditions) over the
central equatorial Pacific (Fig. 4, bottom panel). These conditions are
consistent with the observed decrease in SST anomalies in the central
equatorial Pacific that occurred from December 2003 through March 2004.
A majority of the statistical and coupled model forecasts indicate near
neutral conditions in the tropical Pacific (Niņo
3.4 SST anomalies between -0.5°C
and +0.5°C)
through the northern summer 2004 Thereafter, the forecasts show increasing
spread and greater uncertainty. Given the recent trends and observed oceanic
and atmospheric patterns discussed above, it is likely that ENSO-neutral
conditions will continue for the next 3-6 months.
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
http://www.cpc.ncep.noaa.gov (Weekly Update). Forecasts for the evolution of
El Niņo/La Niņa 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
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