East Asia and Western Pacific METEOROLOGY AND CLIMATE

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recorded on the 27th. The period (15th-24th November) did not
experience any heavy rain in Malaysia because the winter monsoon
was not established yet since the near-equatorial trough was
located north of Malaysia,
The period (15th November - 15th December) can be divided
into 2 periods of different convective activities over Malaysia;
one (15th November - 1st December) with enchanced convective
activity and the other (2nd-15th December) with suppressed
convective activity.
The period of enhanced convective activity is
charaterised by the following synoptic features:-
(i) There were 4 cold outbreaks in China.
(ii) The near-equatorial trough axis was nearly parallel
to the equator from the West Pacific to the South
China Sea with broad zonal easterlis north of it in
the lower and middle troposphere (850 hPa to 500
hPa levels).
(iii) At the 500 hPa level the mid latitude westerlies
over the Asian continent extended southwards to
only 20°N and the subtropical ridge axis was
located between 20° and 15°N.
Figure 2a and b are the streamline analysis respectively
for the 850 and 500 hPa levels for the 26th November 1986 when
heavy rain began to fall in Peninsular Malaysia.
The period of suppressed convective activity is
characterised by the following synoptic features:-
(i) There was only one clod outbreak on the 7th
December 1986.
(ii) During most of the days, the near-equatorial trough
was observed to disappear from the West Pacific -
South China Sea region. Instead, the northeasterly
cross-equatorial flow prevailed over this region.