A leading
US forecaster has contested India Meteorological Department's (IMD) forecast of
monsoon onset on June 1. The Climate
Prediction Centre (CPC) of the US National Weather Services is of the view that
the onset could get delayed.
But it did
not say by what extent.
SUPPRESSED
RAIN
The CPC
made its observations based on its outlook for ‘suppressed convection across
parts of the northern Indian Ocean and southern India' until May end. Suppressed
convection refers to the weakened cloud building activity, and resultant
inability to force the rains.
Northern
Indian Ocean includes and Arabian Sea, the Bay of Bengal and equatorial-central
Indian Ocean to the south of Sri Lanka.
SRI LANKA
ONSET
Meanwhile,
the Sri Lankan Met department has been quoted as saying that the onset of
monsoon over the island nation may not happen ‘until May end.' The normal
onset date here is around May 25, and the local Met Department is of the view
that it may not happen that way.
Sri Lanka
is the penultimate port of call for monsoon before it lashes the southwest
coast of mainland India along Kerala. The culprit
for the delay is a wave that travels high in the atmosphere and periodically
across the Indian Ocean. It transits
from the west (east Africa) and enters the Maritime Continent (Indonesia, et
al) and the Pacific, influencing weather on ground over which it passes.
This is
called the Madden-Julian Oscillation (MJO) wave, and has alternating dry and
wet phases which set up attendant weather over ground.
MAY LINGER
The
prevailing dry phase was expected to move to the east by this time, but the CPC
expects it to linger over equatorial Indian Ocean until May-end.
The eastern
parts of the region would benefit from the stand-off. Not
surprisingly, the CPC signals wet conditions over parts of South-east Asia.
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