Tropical Highlights - July 2003
Current atmospheric and oceanic conditions continue to reflect neutral
conditions across the Tropical Pacific and do not support the development of
La Niņa or El Niņo
during the next few months. Sea surface temperatures (SSTs) were slightly
warmer than average across the western and central Pacific and cooler than
average along the South American coast (Fig. T18). SST anomalies have
increased across the eastern and central equatorial Pacific during the past
two months (Table T2, Fig. T4).
Oceanic thermocline depths, as measured by the depth of the 20°C
isotherm (Figs. T15, T16) remained deeper than average over the
central and western Pacific and shallower than average along the South
American coast. This pattern has been modulated by an eastward-propagating
Kelvin wave during the past two months. Consistent with the conditions
observed during July, oceanic temperatures at thermocline depth were 3-4°C
above average in the central Pacific and 2-3°C
below average in the eastern Pacific (Fig. T17).
The equatorial easterly winds were slightly weaker than average east of
160°W and slightly stronger than
average near the date line (Table T1, Fig. T20) during the
month, while the Tahiti-Darwin SOI was positive (0.2) for the first time
since February 2002 (Table T1, Fig.
Relatively weak outgoing longwave radiation (OLR) anomalies were observed
throughout much of the global Tropics, with the exception of the Indian
Ocean sector (Fig. T25). Enhanced convection (negative OLR anomalies
and above-average precipitation) was observed over the western Indian Ocean
and over the northern portions of the Arabian Sea and parts of the Arabian
peninsula, Pakistan and Northwest India (Figs. E3,
convection (positive OLR anomalies and below-average precipitation) was
found over the eastern Indian Ocean (Fig. T25).