🌧️ IMD Issues Watch for Developing Depression Over South Bay; System May Steer Toward Tamil Nadu–South Andhra Coast

 

Global models raise storm probability to 50% as fresh circulation feeds intensification

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The India Meteorological Department (IMD) has placed the south Bay of Bengal under a depression watch, signalling the beginning of a potentially active weather phase for Tamil Nadu, south Andhra Pradesh, and adjoining regions. The alert follows indications that a low-pressure area will form over the south-east Bay by Saturday and strengthen steadily as it tracks west-northwest.

Likely Path: Toward Tamil Nadu–South Andhra Belt

Once formed, the system is projected to intensify into a depression by Monday, orienting itself toward the Tamil Nadu–south Andhra Pradesh coastline. IMD charts and global numerical models suggest further strengthening over the south-west Bay by midweek, with the system feeding on favourable atmospheric conditions.

Forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) echo the IMD outlook, projecting the depression to pass between the Sri Lanka and Tamil Nadu coasts on Monday morning before deepening.

Cloud Bands Rebuild Over Kerala–Tamil Nadu

Even as the incoming system evolves, an existing low-pressure area—now drifting away toward Lakshadweep and the Maldives—pulled moisture-laden clouds back over Kerala and south Tamil Nadu on Wednesday evening.

A fresh cyclonic circulation has also formed over the south-west Bay, anchored along a trough preceding the expected low-pressure area. Meteorologists expect this circulation to merge with the developing system, adding momentum and mass, and aiding further strengthening as it advances west-northwest.

Global Models Raise Storm Probability

The Climate Prediction Center (CPC) of the US National Weather Service and the ECMWF have raised the probability of a storm forming over the south-west Bay to 40–50%. Meteorologists are monitoring a wide zone—from the western Pacific and South China Sea to the Andaman Sea and Bay of Bengal—for potential storm genesis.

Satellite imagery shows strong convection (thunderstorms and intense rainfall) around the Andaman & Nicobar Islands, driven by vigorous easterly winds streaming in from the heated western Pacific region.

Extremely Heavy Rainfall Already Reported

In the 24 hours ending Wednesday morning, parts of Tamil Nadu, Puducherry, and Karaikal recorded extremely heavy rainfall, triggered by the departing rain-maker low-pressure area that moved from the Comorin region toward Lakshadweep–Maldives.

Heavy to very heavy rain was also widespread across:

• Tamil Nadu, Puducherry & Karaikal

• Kerala & Mahe

• Lakshadweep

• Andaman & Nicobar Islands

And isolated downpours occurred over Coastal Andhra Pradesh, Yanam, Rayalaseema, Coastal Karnataka, and South Interior Karnataka.

Notable Rainfall (10 cm and above)

Tamil Nadu

• Oothu – 23 cm
• Nalumukku – 21 cm
• Kakkachi – 19 cm
• Manjolai – 18 cm
• Ayikudi – 14 cm
• Tenkasi & Tenkasi AWS – 12 cm
• Shencottah – 10 cm
• Kayalpattinam (Thoothukudi) – 10 cm

Kerala

• Kumarakam (Kottayam) – 19 cm
• Kayamkulam (Alappuzha) – 12 cm
• Mattanchery AWS (Ernakulam) – 11 cm
• Vaikom (Kottayam) – 10 cm
• Kayamkulam ARG (Alappuzha) – 10 cm

What’s Next?

With multiple atmospheric triggers aligning, meteorologists expect swift developments over the weekend. The Bay of Bengal will remain under close watch, with coastal districts of Tamil Nadu and south Andhra Pradesh advised to stay alert for further IMD updates as the system intensifies.