A long-anticipated low-pressure area is expected to form over north-west Bay of Bengal off the Odisha and West Bengal coasts by Thursday in what appears to be an emerging and sustained wet spell covering the West Coast, East-Central India, East and North-East India and North-West India, and potentially extending the monsoon to the entire country before the July 8 normal.

Likely longer haul

Numerical projections by the India Meteorological Department (IMD) suggest that an area of interest off the Odisha-West Bengal coast has been hatching for sometime now. Even after formation on Thursday, the ‘low’ will remain on a slow burn, the ideal scenario that can help it operate for a longer haul, which will help the monsoon converge and consolidate.

The workman-like manner in which the ‘low’ operates into the rest of June and early into July may be an unintended kickback from what has been a quieter South China Sea/north-west Pacific. The only storm that falls under the footprint of the same monsoon trough here has been tropical storm Wupet that attained typhoon status briefly ahead of landfall over South China last week.

Quieter Pacific, Atlantic

Incidentally, the storm (typhoon/ hurricane) season over the West Pacific/South China Sea and farther west over the Atlantic has been muted this season. A typhoon in the South China Sea/West Pacific that lies to the east of the Bay of Bengal, cuts both ways; it can help revive the overall monsoon current, but can also spoil it if not ideally oriented, going farther east into the Pacific.

Currently, the South China Sea hosts a depression that may not make much of an impression on proceedings in the Bay; if anything, it is forecast to move north-west towards the south-east China coast, and not away to the east. Tropical storm (depression)Sepat is hovering so far away to the east off Japan that it may not likely harm prospects in the Bay.

Slow monsoon advance

On Wednesday, the IMD said the monsoon has advanced slowly but surely to some more parts of Rajasthan; West Uttar Pradesh; Haryana; and Punjab in North-West India. Conditions are favourable for its further advance to more parts of Rajasthan; Punjab; Haryana; Delhi; and the remaining parts of West Uttar Pradesh by Thursday, with a crucial monsoon trough over land likely unfolding.

An upper level air cyclonic circulation has persisted over north-east Madhya Pradesh. A precursor trough runs from the north-east Arabian Sea to the above cyclonic circulation across south Gujarat and north Madhya Maharashtra. Linking up with the circulation over the Bay, this can potentially activate the monsoon trough, helping the advance of the monsoon over the rest of the country.

Rainfall statistics

Incessant rain over many parts of the country has lifted the overall rainfall to +4 per cent as of Tuesday, though masking significant deficits in individual met subdivisions in Central India and South Peninsula. Extremely heavy rain lashed parts of West Madhya Pradesh and east Gujarat during the 24 hours ending on Wednesday morning, while it was heavy to very heavy rain over Uttarakhand.

Haryana-Chandigarh-Delhi, too, have received heavy rain ahead of the monsoon’s arrival. Heavy rain also lashed Himachal Pradesh; East Rajasthan; East Madhya Pradesh; Madhya Maharashtra; Coastal Karnataka and North Interior Karnataka and elsewhere over East and North-East India; Central India; North-West India; and South Peninsula on Tuesday ahead of the formation of a Bay ‘low.’

Published on June 25, 2025