Tropical Highlights - November 2003

Surface and sub-surface oceanic conditions across the Tropical Pacific continued to trend towards a weak warm episode during November 2003 (Table T2), while atmospheric features continued to reflect ENSO-neutral conditions (Table T1). Sea surface temperature (SST) anomalies remained above normal across the entire equatorial Pacific during November (Fig. T18), with the largest departures (exceeding 1�C) observed in the western and central Pacific. For the Ni�o-4 region, which spans the central equatorial Pacific, SST departures reached their highest values since February 2003 (Table T2, Fig. T5).

Oceanic thermocline depths, measured by the depth of the 20�C isotherm (Figs. T15, T16), remained slightly deeper than average across most of the equatorial Pacific during November. Consistent with these conditions, oceanic temperatures at thermocline depth were 1-2�C above average across most of the equatorial Pacific (Fig. T17).

The low-level and upper-level equatorial winds remained near average across the tropical Pacific during November (Table T1, Figs. T20, T21), and the Tahiti-Darwin SOI remained near zero (-0.4) (Table T1, Fig. T1). Also, relatively weak Outgoing Longwave Radiation (OLR) anomalies were observed throughout much of the global Tropics, although convection was suppressed near the date line and enhanced over the western Pacific (Fig. T25). Since September there has been a tendency for convection to be enhanced over the equatorial Pacific between 130�E and 160�E (Fig. T11). None of these indicators has exhibited any trend towards a warm or cold episode during the past six months, and all are consistent with ENSO- neutral conditions.