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HOME > Expert Assessments > Climate Diagnostics Bulletin > Tropical Highlights

Tropical Highlights - January 2005

Positive sea surface temperature (SST) anomalies persisted across the central and east-central equatorial Pacific during January 2005.  The SST anomalies in the eastern equatorial Pacific have decreased slightly, with a January value of -0.1 in the Niņo 1+2 region (Fig. T18, Table T2).  The pattern of tropical SSTs during January 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 decreased to 0.6 (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 0.3, Table T1, Fig. T1) was positive for the first time since May 2004.  

The oceanic thermocline, measured by the depth of the 20°C isotherm, remained deeper than average across most of the equatorial Pacific during January (Figs. T15, T16). Consistent with these conditions, oceanic temperatures at thermocline depth were 2-3°C above average across most of the 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 January 2005, except that low-level westerly anomalies (more than 3.0 m s-1) were observed over the western equatorial Pacific and Indian Ocean , and low-level easterly anomalies (more than 3.0 m s-1) over central equatorial Pacific  (Fig. T20). The global Tropics featured near-average convection, with the exception of enhanced convection over the western equatorial Pacific and over portions of the tropical North Atlantic and northern South America (Fig. T25), where extreme flooding occurred in Guyana during the last half of January. 

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