IMD update: Isolated very heavy rain for TN, Puducherry for two more days

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India Meteorological Department’s numerical projections indicate possibility of rapid intensification of the Bay system into a tropical cyclone, although it has yet to take an official call on this

By Vinson Kurian

Updated - October 20, 2026 at 05:16 PM. | Thiruvananthapuram

Heavy cloud banks developed off the south Andhra Pradesh coast, south-east Tamil Nadu and southern parts of Bay of Bengal as the Bay waters braced for a big churn into second half of the week. | Photo Credit: https://zoom.earth

Isolated very heavy rainfall is forecast over Tamil Nadu, Puducherry and Karaikal on Wednesday and Thursday, as the India Meteorological Department (IMD) watches the possible formation of two low-pressure areas at opposite ends of the Bay of Bengal, one of which could likely intensify into a tropical cyclone.

The first low is expected to form over the south-west Bay and adjoining Tamil Nadu coast on Wednesday, as a cyclonic circulation descends to lower atmospheric levels. The European Centre for Medium-Range Weather Forecasts (ECMWF) had earlier suggested the system could instead form over the south-east Arabian Sea.

Andaman Sea system

The second system is expected to emerge from an incoming circulation over the Gulf of Thailand and adjoining parts of Thailand and Myanmar. Moving into the north Andaman Sea by Wednesday, it is forecast to travel west-north-west and form a low over the south-east and adjoining east-central Bay by Friday. It could then turn north-westwards towards the Andhra Pradesh coast and intensify further.

IMD’s numerical projections indicate possibility of its rapid intensification over the warm waters into a tropical cyclone, although it has yet to take an official call. Global model forecasts, including those of the ECMWF, broadly support this scenario, against the backdrop of an active north-east monsoon, a passing helpful Madden-Julian Oscillation (MJO) wave over Indian Ocean and a developing positive Indian Ocean Dipole (IOD) phase.

Heavy overnight rain

The evolving systems are already influencing regional weather. On Tuesday evening, an elongated trough of low pressure extended from the circulation over south-west Bay and adjoining Tamil Nadu coast towards north coastal Andhra Pradesh. Its southern flanks overlapped the leading edge of an easterly wave advancing from the Andaman Sea, within which the incoming disturbance from the Gulf of Thailand is expected to be embedded.

The IMD has issued a fishermen’s warning for the Andaman Sea for three days from Friday, coinciding with the anticipated intensification phase of the system embedded in the easterly wave. Meanwhile, heavy rain battered parts of the Andaman and Nicobar Islands during the 24 hours ending Tuesday morning, with Nancowry recording 7 cm. Several mainland locations reported higher totals.

Heavy rain in Kerala, TN

Among the significant rainfall recordings were Kozhikode (10 cm) and Vaikom (6 cm) in Kerala; Brahmavar AWS (8 cm) in coastal Karnataka; and Tiruvadanai and Thalaignayer (8 cm each) in Tamil Nadu. Chittampatti, Ramanathapuram, Devakottai, Manamadurai, Tirupathur and Thanjai Papanasam recorded 6 cm each. Lanja in Ratnagiri district, Maharashtra, also received 6 cm.

The IMD expects heavy rain to persist across much of the southern peninsula over the coming days. Kerala and Mahe are likely to receive isolated heavy rainfall for six days; Tamil Nadu, Puducherry and Karaikal for four days from Friday; and South Interior Karnataka for four days from Wednesday. Lakshadweep is likely to see heavy rain for five days from Thursday, with coastal Karnataka on Saturday. Coastal Andhra Pradesh, Yanam and Rayalaseema are also forecast to receive heavy rain on Wednesday.

Published on October 20, 2026

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