Tropical Highlights - December 2005

 

Sea surface temperature (SST) anomalies remained negative in the eastern tropical Pacific during December 2005, with a December value of -0.6 in the Niño 3.4 region and -0.7 in the Niño 1+2 region (Fig. T18, Table T2). The Tahiti - Darwin SOI (latest value -0.2, Table T1, Fig. T1) was slightly negative, primarily in response to higher-than-average pressure over Darwin . Meanwhile, the equatorial SOI for December is +2.2 (Fig. T2). The equatorial SOI has been greater than or equal to +0.5 since September 2005.

The oceanic thermocline, measured by the depth of the 20°C isotherm along the equator, featured near-average depth in the central Pacific and slightly shallower-than-average depth in the eastern Pacific during December (Figs. T15, T16). Consistent with these conditions, equatorial oceanic temperatures at thermocline depth were near average throughout most of the Pacific and 2-3^oC below average in the eastern Pacific (Fig. T17).

During December, near-average low-level winds were observed over the eastern equatorial Pacific while low-level easterly anomalies (more than 3.0 m s^-1) were observed over the central and western equatorial Pacific (Fig. T20). In the global tropics, enhanced convection (above-average rainfall amounts) was observed over the eastern Indian Ocean , across Indonesia , as well as over the northeastern Brazil (Figs. T25, T26 and E3).