surface temperature (SST) anomalies remained positive across the central and
east-central equatorial Pacific during October 2004.
The SSTs in the eastern equatorial Pacific have increased from below
average to near average, with an October value of 0.0 in the Niņo 1+2
region (Fig. T18, Table T2).
The pattern of Tropical SSTs during October featured positive
anomalies greater than +1.0°C between 160°E and 150°W (Fig.
T18). The SST anomaly in
the Niņo 3.4 region remained 0.8, the highest value since January 2003, and
the Niņo 4 anomaly remained 1.1, the highest value since November 2003 (Table
atmospheric features continued to show month-to-month variability associated
with intraseasonal (Madden-Julian Oscillation - MJO) activity (Figs. T11,
T12, T13, Table
oceanic thermocline, measured by the depth of the 20°C
isotherm, remained deeper than average in the western and central Pacific
and deepened in the eastern Pacific during October (Figs. T15,
T16). Consistent with these conditions, oceanic
temperature anomalies at thermocline depth increased to 2-3°C
above average in the eastern equatorial Pacific (Fig.
monthly low-level (850-hPa) and upper-level (200-hPa) equatorial zonal wind
indices, the Tahiti-Darwin SOI and the outgoing longwave radiation (OLR)
index have all exhibited considerable variability since November 2003 in
association with intraseasonal (Madden-Julian Oscillation) activity (Table
October, near-average low-level winds were observed over the central and
eastern equatorial Pacific while low-level westerly anomalies (more than 3.0
m s-1) were observed over the western equatorial Pacific (Fig.
T20). The global Tropics featured near-average convection, with the
exception of enhanced convection over the
(Fig. T25). The
- Darwin SOI was -0.3
(Table T1, Fig. T1),
and the equatorial SOI remained -0.2 (Fig. T2).
The Tahiti-Darwin SOI has been negative during the past 5 months, in
response to higher-than-average pressure over