A fresh low pressure area is expected to form over the southeast and adjoining Bay of Bengal within the next 48 hours under the influence of an Equatorial Rossby wave. This development, combined with a strengthening Madden Julian Oscillation (MJO) over the East Indian Ocean, is poised to bring a significant boost to the Northeast Monsoon over Tamil Nadu, particularly the north coastal districts and the Cauvery delta region.
Drivers Behind the System
The Equatorial Rossby wave and the MJO are forecast to interact over the East Indian Ocean in the coming days. The MJO is likely to strengthen in this region, creating a favourable environment for the low to organise and intensify further. Unlike the recent cyclones Arnab and Murasu, which had more northerly or different tracks, the genesis of this system is expected to be positioned further south and west closer to the central parts of the south Bay of Bengal.
Strong ridge alignment are also establishing, which should help steer the system initially westward before it takes a west-northwest trajectory toward the North Tamil Nadu coast.
Expected Movement and Impact
The low is anticipated to evolve into a rain-bearing system of the season. As it tracks toward North Tamil Nadu, the Northeast Monsoon is likely to enter a vigorous phase over the north coastal Tamil Nadu and Cauvery delta districts from around mid November.
Looking further ahead, standing wave conditions over the East Indian Ocean are expected to support a series of back to back three low pressure developments over the south Bay of Bengal through the end of November. This sequence suggests the Northeast Monsoon is heading into its peak phase of the year within the next week or so, bringing enhanced rainfall opportunities to the region after earlier systems.
Advisory for Coastal Communities
Coastal fishermen are advised not to venture into the deep sea from 14 November. Those already at sea are strongly urged to return to shore on or before the night of 13 November. Sea conditions are expected to deteriorate as the system organises.
Stay tuned for updates as the low develops.
