East Asia and Western Pacific METEOROLOGY AND CLIMATE

69
WIND AND MOISTURE FIELDS DURING THE PERIODS OF ENHANCED AND
SUPPRESSED CONVECTIVE ACTIVITY OVER THE MALAYSIA-SOUTH CHINA SEA
REGION DURING THE NORTHERN WINTER MONSOON, NOVEMBER-DECEMBER 1986
ABSTRACT
By
Boon-Khean Cheang and Prakash Sankaran
Malaysian Meteorological Service
From the 1986 upper air streamline analyses, two synoptic
patterns for the interaction of cold surges with the tropical
circulation during the northern winter monsoon were identified.
The
first pattern is associated with the occurrence of widespread
heavy rain in the Malaysia-southern South China Sea region.
second pattern is associated with the occurrence of widespread
heavy rain in Philippines-West Pacific region and suppressed
condition in Malaysia-southern South China Sea region. The main
distinction between these two patterns is the presence (absence) of
deep and broad zonal easterlies In the tropics in the first
(second) pattern. The tropics in this report is referred to the
region from the West Pacific to Southeast Asia. Moisture flux was
computed for the period, 15 Nov - 15 Dec 86.
The
Latitude-time section
of the flux at 850, and 500 hPa levels are presented and discussed
in the report.
1.0 INTRODUCTION
Malaysia-southern
Enhancement of eonvective activity over the
South China Sea region due to interaction of cold
surges and tropical circulation during the northern winter monsoon
has been documented In many studies (Ramage 1971, Cheang 1976,
Chang et al 1979 and others).
Nevertheless supressed convective
activity over the same region due to interaction of cold surges and
tropical circulation has yet to be documented.
This report presents two examples of interaction of cold
surges and tropical circulation bringing about different weather
conditions in Malaysia December 1983 and November and December
1986.