North-east monsoon may arrive by Oct 15 as predecessor season hastens withdrawal
The June-September south-west monsoon may complete its withdrawal and exit the land towards the second week of October, which will likely set the stage for the arrival of the north-east monsoon over Tamil Nadu, Kerala, and parts of Andhra Pradesh around October 15, India Meteorological Department (IMD) has said in a weather outlook for the next fortnight.
Reversal of seasonal winds
Numerical model predictions suggest the south-westerly winds will gradually give way to north-easterlies from midweek next week (October 8-9). Except for occasional blips, this tendency shows signs of entrenching over the Bay of Bengal, South Peninsula and the Arabian Sea during the subsequent three-four days until an easterly wave front-ended by a cyclonic circulation in the Bay and a counterpart circulation in the Arabian Sea likely heralds the north-east monsoon.
Above normal rainfall
The IMD has gone on record saying seasonal rainfall between October and December (north-east monsoon period) over the South Peninsula that includes Kerala, Tamil Nadu, and Andhra Pradesh, is expected to be above normal, amounting to 112 per cent of the long-period average of 33.4 cm. This is the major season rain, particularly for meteorological subdivisions of Coastal Andhra Pradesh, Rayalaseema and Tamil Nadu-Pondicherry.
For Interior Karnataka, Kerala and Lakshadweep- which made maximum gains during the preceding south-west monsoon- rainfall continues till December. The north-east monsoon contributes about 20 per cent of the annual total to these meteorological subdivisions.
Low-pressure area soon
Meanwhile, the IMD has retained the watch for formation of the first post-monsoon low-pressure area over coastal areas of West Bengal and adjoining south-west Bangladesh any time. A preparatory circulation persisted over south-west Bangladesh, with a trough extending from north-east Bihar to the north Andaman Sea passing through it on Friday morning. It will descend to lower levels to form the ‘low’. Another cyclonic circulation hung over Lakshadweep and neighbourhood.
Isolated heavy rainfall likely
Isolated heavy rain is likely over Tamil Nadu and Kerala during the week starting October 10. Alongside, scattered to fairly widespread rain may break out over Central, East & Northeast India and the South Peninsula. It will be Isolated heavy to very heavy over East & North-East India across Arunachal Pradesh, Assam & Meghalaya and the hills of West Bengal & Sikkim and isolated heavy over the plains of West Bengal, Odisha, Jharkhand, and Bihar.