A preparatory cyclonic circulation has dropped anchor over South-West Bay of Bengal and adjoining Equatorial Indian Ocean (off the Sri Lanka coast) under whose influence a low-pressure area is likely to form over the same region during the next two days. It will amplify the flow of rain-bearing winds towards Tamil Nadu even as it approaches the Tami Nadu-Puducherry coast.

India Meteorological Department (IMD) said that the track towards North-West shall take the ‘low’ towards Tamil Nadu-Puducherry coasts by Friday. It could undergo intensification thanks to the warmth of the ocean waters in the vicinity. Wind-field projections suggest that it could strengthen to become a depression, if all conditions remain the same during the next couple of days.

Trigger to next wet spell 

Fairly widespread to widespread light to moderate rainfall with isolated heavy falls, thunderstorms and lightning is likely over Tamil Nadu, Puducherry and Karaikal from Thursday to Saturday, and over Rayalaseema and South Andhra Pradesh on Friday and Saturday. Isolated very heavy rainfall is also likely over Tamil Nadu, Puducherry, Karaikal, Rayalaseema and South Andhra Pradesh on these days. 

Squally winds with speed reaching 45-55 kmph gusting to 65 kmph (near-cyclonic strength) will prevail over the South-West Bay and Sri Lanka coasts on Thursday; and over the South-West Bay, the Gulf of Mannar, and along and off the Tamil Nadu-South Andhra Pradesh coast on Friday and Saturday. Fishermen are advised not to venture in to these areas during the same period. 

Western disturbances

To the North of the country, a couple of rain-maker western disturbances travelling from Afghanistan-Pakistan into North-West India are forecast to trigger helpful winds and showers. This could clean up the air over the region to some extent. The first disturbance was spotted in the form of a trough over East Pakistan on Tuesday, and has already started impacting the weather on this side of the international border. The succeeding disturbance is expected to affect the region from Wednesday. 

The IMD has forecast scattered to fairly widespread, light to moderate rainfall or snowfall over Jammu, Kashmir, Ladakh, Gilgit-Baltistan and Muzaffarabad for three days from Tuesday; over Himachal Pradesh on Wednesday and Thursday; and isolated light to moderate rainfall or snowfall over Uttarakhand on Wednesday. Isolated to scattered light rainfall or drizzle is likely over Punjab, Haryana, Chandigarh and Delhi until Thursday and over West Rajasthan on Wednesday. 

November rain outlook

Meanwhile, the IMD has forecast that November will see above-normal rainfall (greater than 123 per cent of the long-period average) over the South Peninsula consisting of five meteorological sub-divisions of Tamil Nadu, Puducherry and Karaikal; Coastal Andhra Pradesh and Yanam; Rayalaseema, Kerala and Mahe; and South Interior Karnataka. The spatial distribution suggests normal to above normal rainfall for most parts of the country except some areas of South Peninsula (Coastal Andhra Pradesh), North-West India and North-East India where below normal rainfall is likely. 

What lends credence to this outlook is the latest update from the Australian Bureau of Meteorology which said that the La Niña has maintained its intensity in the tropical Pacific. The negative Indian Ocean Dipole (IOD) too persists, with the latest weekly ocean index showing neutral values for the first time since June. But cloud and rainfall patterns remain typical of a negative IOD. La Niña and a negative IOD are not the best advertisement for a good North-East monsoon, though with exceptions.