Monsoon reaches south Bay of Bengal, Nicobar Islands: IMD

The southwest monsoon advanced into parts of the south Bay of Bengal, south Andaman Sea, Nicobar Islands and some areas of the north Andaman Sea on Tuesday, 13 May, the India Meteorological Department said.

The weather department said moderate to heavy rainfall lashed Nicobar Islands over the past two days.

About Advance of Southwest 2025 on 13th May 2025:

1) Widespread moderate rainfall with heavy rainfall at a few places occurred over the Nicobar Islands during past 24 hours. Thus, the widespread rainfall with isolated/scattered heavy rainfall continued over the Nicobar Islands… pic.twitter.com/JyabwSPGIc

— India Meteorological Department (@Indiametdept) May 13, 2025

The strength and depth of westerly winds over the south Bay of Bengal, Nicobar Islands and Andaman Sea increased in this period, with wind speeds exceeding 20 knots at 1.5 km above sea level and extending up to 4.5 km in some areas.

The Outgoing Longwave Radiation (OLR), an indicator of cloudiness, also decreased over the region. These conditions met the criteria for the monsoon's onset over the region, it said.

The weather office said conditions are favourable for the monsoon to advance further into more parts of the south Arabian Sea, Maldives and Comorin area; more areas of the south Bay of Bengal; the entire Andaman and Nicobar Islands; remaining parts of the Andaman Sea; and parts of the central Bay of Bengal over the next three to four days.