Withdrawal of SW Monsoon
a)
Withdrawal
from extreme north-western parts of the country is not attempted before 1st
September.
b)
After
1st September:
The following major synoptic features are considered
for the first withdrawal from the western parts of NW India.
i) Cessation
of rainfall activity over the area for continuous 5 days.
ii) Establishment
of anticyclone in the lower troposphere (850 hPa and
below)
iii) Considerable
reduction in moisture content as inferred from satellite water vapour imageries
and tephigrams.
Further Withdrawal from the Country
i)
Further withdrawal from the country
is declared, keeping the spatial continuity, reduction in moisture as seen in
the water vapour imageries and prevalence of dry weather for 5 days.
ii) SW monsoon is from the southern peninsula
and hence from the entire country only after 1st October,
when the circulation
pattern indicates a change over from the southwesterly
wind regime.