Close on heels of likely low pressure area in the Arabian Sea, yet another weather system may come up in Bay of Bengal, as well. Southwest monsoon withdrawal is expected to be completed in the next about 2 days. Following withdrawal, Bay of Bengal gears up for ushering of northeasterly winds, a precursor to the arrival of winter monsoon over South Peninsula. Bay of Bengal (BoB) at the moment is very turbulent, a very common feature during the transition from southwest to northeast monsoon.
Currently, there is a cyclonic circulation over deep areas of southwest BoB and another one coming up over eastern parts of BoB. Under the combined influence, a broad cyclonic circulation, mostly oriented east-west, is visibly coming up over the central and adjoining southern parts of BoB. This looks to be getting more organized and also shifting bit closer to the Tamil Nadu coast over the next 48 hours.
A low pressure area is anticipated to form over southwest BoB on 18thOctober, at a safe distance from Tamil Nadu coast. This weather system is likely to meander over the same region in the subsequent 72 hours. The feature may not cause any heavy rains over Tamil Nadu because of adequate distance but will surely align the northeasterly flow of winds, prerequisite for setting of northeast monsoon.
The scheduled arrival date of the northeast monsoon is 20th October. This is likely to get delayed. However, the presence of cyclonic circulation followed by a low-pressure area will stimulate the easterly stream over BoB. Light to moderate rainfall is quite likely over Coastal Tamil Nadu and South Coastal Andhra Pradesh during this week but may not suffice for typical onset of northeast monsoon.