No. IV-18.4 - (IMD), Pune

45
data showed that though there was no temperature discontinuity across the
trough line, the southeasteries to the east of the trough line, were considerably
moist and the northeasterlies to the west of the trough were
dry. Rainfall was confined to the moist southeasterlies on the eastern
side of the trough line.
iii) Though initially when the low pressure area was out at sea in the Bay,
the westerlies over the Peninsula Were moderate to strong, subsequently
when the system moved inland, the easterlies to the north of the low
became quite strong (reaching upto 35 kts) in the lower troposphere while
the westerlies were relatively weak.
iv) Rainfall extended far to the north of the low in the field of the moist
easterlies and the significant amounts were close to the low or to the
north of it, in the field of the southeasterlies. Coastal Andhra Pradesh
which was well to the north of the low got vigorous monsoon on two consecutive
days and heavy falls upto 12 cms were recorded there. The rainfal
to the north of the low was confined to the area of cyclonic shear in the
easterlies.
v) The contrast in the rainfall and wind patterns on 7th and 8th when compared
to 10th and llth show the differences between the two situations:
a) linen the low was out at sea with only a east-west oriented trough line
across the south Peninsula and
b) when the well-marked low moved across the Peninsula.
vi) Rainfall was generally accompanied by thunder.
vii) The vertical time sections of Port Blair (Fig. 16.10) and Madras
(Fig. 16.11) showed the passage of the low. The forward slope of the
axis of the low with height, in both the sections, may be noted.
Similarly, the strengthening of the southeasterlies after the low passed
over the station is also noteworthy.
viii).The isobaric field, 24 hr. pressure changes and the changes in the upper
winds gave good indications of the movement of the low; similarly the