Sea surface temperature (SST)
anomalies remained positive across the central equatorial Pacific and
negative in the eastern equatorial Pacific during March 2005, with a March
value of 0.4 in the Niņo 3.4 region and -0.9 in the Niņo 1+2 region (Fig.
T18, Table T2).
Meanwhile, atmospheric features continued to show month-to-month variability
associated with intraseasonal (Madden-Julian Oscillation - MJO) activity (Figs.
T11, T12, T13,
Table T1). The Tahiti - Darwin SOI (latest
value -0.2, Table T1, Fig. T1)
was slightly negative, primarily in response to higher-than-average pressure
The oceanic thermocline,
measured by the depth of the 20°C isotherm, remained deeper than average
across the central and east-central equatorial Pacific and shallower than
average in the eastern equatorial Pacific during March (Figs. T15,
T16). Consistent with these conditions,
oceanic temperatures at thermocline depth were 2-6°C above average across
the central equatorial Pacific and 2-4°C below normal in the eastern
equatorial Pacific (Fig. T17).
The 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 January 2004 in association with
intraseasonal (Madden-Julian Oscillation) activity (Table T1).
Near-average low-level winds were observed over
most of the tropical regions during March 2005, except that strong low-level
westerly anomalies (more than 3.0 m s-1) were observed
over the eastern equatorial Pacific (Fig. T20).
The global Tropics featured enhanced convection over the eastern tropical
Pacific (near the west coast of Central America) and near-average convection
elsewhere (Fig. T25).