Depression over southwest Bay of Bengal(BoB) moved northwest to come closer to Tamil Nadu and Andhra Pradesh coast. It is centred around 12.1deg North and 84.3deg East in the morning, about 400km east-southeast of Chennai. The system will continue to move northwest and reach closer to the coast covering another 200km by tomorrow morning. However, it is showing signs of weakening as it nears North Tamil Nadu and South Andhra Pradesh coast.
The low pressure area had earlier come up over Southeast BoB on 18th Nov and became well marked on 19th Nov. It strengthened further to a depression yesterday over southwest BoB and likely to retain its intensity for another 12 hours.
Sea surface temperature is decreasing to about 28 degrees Celsius over southwest BoB and further down to about 27 degrees closer to the coastline. Accordingly, the heat potential is reducing to degrade the weather system. As such, proximity of land increases friction and enhances entrainment. Depression is expected to weaken to a low pressure area by midnight or early morning tomorrow.
Under the influence of this system, spike in Northeast Monsoon activity is expected over Tamil Nadu and Andhra Pradesh. Moderate to heavy rains are likely over extreme North Tamil Nadu and South Coastal Andhra Pradesh. Chennai, Kanchipuram, Tambaram, Nellore, Ongole, Kavali, Bapatla and Machilipatnam can expect few spell of heavy rains, moderated by intermittent light spell, in between. Weather activity is likely to last for 3 days, between 21st and 23rd Nov.
The low pressure will gradually move eastward across South Peninsula to shift over to the Arabian Sea on 24th Nov. Weakened system as cyclonic circulation will continue moderate rain and thundershowers over interior Tamil Nadu, farthermost parts of South Interior Karnataka and northern half of Kerala on 24th and 25th Nov. Weather activity will turn very light and nearly insignificant from 26th onward.