Conditions are favourable for the withdrawal of the South-West monsoon from the entire country during the next two days. This will set the ground ready for the North-East monsoon or the monsoon in reverse. On Friday, India Meteorological Department (IMD) said the withdrawal line linked Kakinada, Ramagundam and Buldana with Dahanu, advancing deeper into Peninsular India.
Fast-paced evolution
Also on Friday, the IMD said the transformation of the low-pressure area over the South-East Bay of Bengal to a cyclone would be fast-paced to become a depression on Saturday, a deep depression on Sunday and a cyclone (to be named Sitrang, suggested by Thailand) on Monday. It will approach the near West Bengal-Bangladesh coast the very next day. The time and location of the landfall have not been disclosed yet.
The existing ‘low’ will bring fairly widespread to widespread light to moderate rainfall with isolated heavy falls, thunderstorms and lightning over Tamil Nadu, Puducherry, Karaikal, Kerala and Mahe until Sunday. Scattered to fairly widespread rainfall with isolated heavy falls is likely over Odisha from Sunday to Tuesday as the cyclone steams in. Similar weather is forecast for the plains of West Bengal from Monday to Wednesday. Isolated very heavy rainfall is likely over Odisha on Monday and over the plains of West Bengal on Tuesday.
Wet spell for North-East
Fairly widespread to widespread light to moderate rainfall with isolated heavy falls is likely over Assam, Meghalaya and Nagaland, Manipur, Mizoram and Tripura from Monday to Wednesday and over Arunachal Pradesh on Tuesday. Isolated, very heavy rainfall is expected over Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura on Tuesday and Wednesday.
It is to be yet seen whether the frenetic pace will allow the would-be cyclone to stay long enough to intensify multiple rounds as has happened in both the Bay and the Arabian Sea in the recent past. The sea surface to the northern half of the Bay is suitably warm, and the cyclone has enough distance to travel before making landfall. The waters are warmer towards the Sunderbans-Bangladesh coast, where it is ultimately headed. Two factors that could cap the cyclone’s intensification are its fleet-footed nature and wind shear values.
Marginally favourable
The shear values (change in wind speed and direction with height) are marginally favourable at the current location but neutral towards the northern Bay except in the Head Bay and closest to the coast. Tracker models expect these conditions to turn favourable and allow for calibrated intensification.
Meanwhile, on Friday, the IMD said in an extended forecast that a second cyclonic circulation is likely to develop over East-Central Bay during the week from October 27 to November 2. Also, an easterly wave will trigger the light to moderate to scattered to fairly widespread rainfall over most parts of the South Peninsula. Isolated heavy rain is likely to occur over South-East Peninsula (mainly Tamil Nadu, Puducherry and Karaikal) on many days during the week.