The North-East monsoon has set in over the south-east peninsula (mainly Tamil Nadu and coastal Andhra Pradesh) on Tuesday with India Meteorological Department (IMD) announcing predecessor South-West monsoon has withdrawn from the entire country.
Heavy to very heavy rain was reported from coastal Andhra Pradesh & Yanam and Tamil Nadu, Puducherry & Karaikal; while it was very heavy over Rayalaseema and Kerala & Mahe. It was isolated heavy to very heavy over Tamil Nadu & Puducherry; coastal Andhra Pradesh; Rayalaseema; and Kerala until Tuesday morning. Elsewhere in the south peninsula, it was fairly widespread to widespread to moderate. Parts of Maharashtra and adjoining West India, too, witnessed moderate to heavy rain.
Extremely heavy rain
Isolated extremely heavy rain may continue to lash Tamil Nadu, Puducherry & Karaikal; Rayalaseema, coastal Andhra Pradesh & Yanam on Wednesday. It will be very heavy over Tamil Nadu, Puducherry & Karaikal; Kerala & Mahe; south interior Karnataka until Thursday; Rayalaseema, coastal Andhra Pradesh & Yanam; and coastal Karnataka on Wednesday.
Isolated heavy rain is likely over Kerala & Mahe; Tamil Nadu, Puducherry & Karaikal; coastal Andhra Pradesh & Yanam; Rayalaseema; and south interior Karnataka until Thursday; Coastal Karnataka until Friday; and north interior Karnataka on Wednesday and Thursday.
Depression soon over Bay
Arrival of the North-East monsoon was hastened by a well-marked low-pressure area over the central parts of south Bay of Bengal that also helped establish seasonal easterly to northeasterly winds over the south peninsula, south and adjoining central Bay. The well-marked ‘low’ may intensify as a depression by Wednesday and power the flows further towards Tamil Nadu, Puducherry and adjoining south Andhra Pradesh coasts. A helpful baby cyclonic circulation lurked over the nearby west-central Bay.
May cross Chennai coast
Numerical weather model predictions indicate that the depression may cross the Chennai coast by Thursday, continue across the peninsula, and enter the Arabian Sea off the Kerala-Karnataka coasts. This system will leave behind a long trough extending back into the southeast Bay of Bengal, allowing easterly winds to channel moisture and bring rain to the Tamil Nadu coast through midweek next week.
A predecessor but away-going depression over the Arabian Sea to the other side of the peninsula had done its bit to reverse flows from being south-westerly to seasonally north-easterly. On Tuesday, it was moving further away, towards the Oman coast, the IMD said in the afternoon update.
Outlook for the next few days said fairly widespread to widespread to moderate rain may lash Kerala & Mahe and Karnataka for an entire week while it will be scattered to fairly widespread to moderate over Lakshadweep, Rayalaseema, coastal Andhra Pradesh & Yanam, Telangana, Tamil Nadu, Puducherry & Karaikal.