Wednesday’s well-marked low-pressure area over south-west Bay of Bengal drifted further away to lie over south-west adjoining west-central Bay, 317 km south-east of Chennai on Thursday afternoon. The system may move nearly north-west towards north Tamil Nadu and south Andhra Pradesh coast initially, and nearly northwards thereafter, along the Andhra Pradesh coast till Friday.
An India Meteorological Department (IMD) update said the well-marked ‘low’ brought rain to many places over Coastal Andhra Pradesh and Yanam during the 24 hours ending Thursday morning. It also rained at a few places over Lakshadweep and the Andaman and Nicobar Islands and at isolated places over Tamil Nadu, Puducherry and Karaikal, Kerala and Mahe, Rayalaseema, and Odisha.
Heavy rain over north TN
Heavy rain was confined to North Tamil Nadu, with Zone-5 Basin Bridge and Zone-1 Kathivakkam (both in Chennai) recording 7 cm each. The IMD has forecast light to moderate rain at a few places over coastal Andhra Pradesh on both Thursday and Friday and heavy rain at isolated places.
The IMD said light to moderate rain is likely at a few places over north Tamil Nadu, Puducherry and Rayalaseema on Thursday and Friday; and at a few places over coastal Odisha and coastal West Bengal on Friday and Saturday; over Assam & Meghalaya for three days from Saturday; and over Nagaland, Manipur, Mizoram & Tripura for five days from Friday.
Easterly wave on?
Numerical model predictions from IMD and a few global models said the low-pressure area may weaken over west-central Bay but its tail will cosy up to an easterly wave/weather-making trough to trigger sporadic showers along the East Coast (mainly coastal Andhra Pradesh-Odisha). Isolated showers may return to parts of coastal Tamil Nadu from midweek next week.
This may materialise in conjunction with the arrival of an active western disturbance over North-West India, whose long limb is forecast by the European Centre for Medium-Term Weather Forecasts (ECMWF) to descend to the South Peninsula. Associated westerlies may interact with easterlies from the Bay and line up thundershowers along a north-south axis over the region.
Fresh rain clouds likely
The IMD has already set up a watch for the disturbance, which will impact the hills and plains of North-West India from December 27. Thundershowers over the South Peninsula may not last for long, but ECMWF has hinted at deep but broken parcels of rain clouds moving in west-northwest from the Gulf of Thailand, Sumatra, and south-east and south-west Bay the same day.