Tropical Highlights - March 2006

 

The pattern of global tropical sea surface temperature (SST) anomalies during March featured negative anomalies in the east-central equatorial Pacific, with SST anomalies of -0.6 in the Niño 3.4 and Niño 3 regions (Fig. T18, Table T2). Meanwhile, the SST anomalies in the Niño 1+2 region remained slightly positive (Fig. T18, Table T2). The Tahiti - Darwin SOI (latest value 1.4, Table T1, Fig. T1) was positive, in response to higher-than-average pressure over Tahiti and lower-than-average pressure over Darwin (Fig. T19). The latter is consistent with enhanced convection over the western tropical Pacific, including northern Australia during March (Fig. T25).

The oceanic thermocline, measured by the depth of the 20°C isotherm along the equator, featured deeper-than-average depth in the western-central Pacific and shallower-than-average depth in the eastern Pacific during March (Figs. T15, T16). Consistent with these conditions, equatorial oceanic temperatures at thermocline depth were 1-2^oC above average across the western-central equatorial Pacific and 2-5^oC below average across the eastern equatorial Pacific (Fig. T17).

During March, low-level easterly anomalies (more than 3.0 m s^-1) were observed over the central equatorial Pacific, just south of the Equator, and westerly anomalies were observed over Indonesia (Fig. T20). Enhanced convection (above-average rainfall amounts) was observed over Indonesia , northern Australia and the Philippines , while suppressed convection occurred over the central and east-central equatorial Pacific (Figs. T25, T26 and E3). These features are consistent with cold (La Niña) conditions.