Rain Battered Tamil Nadu saw a marked reduction in rains yesterday. In particular North Tamil Nadu saw pretty much a complete cessation of rainfall activity with bright sunshine seen right through the day. With similar pattern likely to prevail for the next couple of days the residents of Chennai will be extremely relieved to see a few days of dry weather continuously in what could be only the second time since mid November both the IMD observatories at Chennai does not record any rains for two consecutive days.
Meanwhile the Low Pressure near Andaman Islands in Bay of Bengal has intensified into a Well Marked Low & is likely to intensify into a Depression in the next 12 to 24 hours. Now in the open waters in a zone where shear has slightly eased, the next 24 to 36 hours is likely to be the golden period for this disturbance as it tries to become the first named cyclone of the Northeast Monsoon season this year.
A lot of you have asked about why the current disturbance is expected to move NW towards Coastal AP while from a similar area of genesis Cyclones Vardah & Gaja moved towards Coastal Tamil Nadu. The interplay between the two ridges on either side of the Indian Sub Continent are the primary riders of the cyclonic systems that form during the Post Monsoon Season. In both the instances of Vardah & Gaja the influence of the Ridge to the West of Indian Sub Continent was seen which created either a Westward track or a last minute WSW dip in the case of Gaja.
In the current case weather models indicate the Bay Disturbance to be firmly under the guidance of the Ridge to the East of Indian Sub Continent which will ensure the depression tracks along its periphery in a WNW movement initially & subsequently a NW & a possible NE recurve. Additionally the arrival of back to back Westerly troughs will also play a role in dragging the convection along with it towards NE india leaving what could be only a skeleton of the system to wash ashore over East India.
As far as rain prospects for today goes parts of South Tamil Nadu is likely to see moderate rains with places along the Western Ghats in the districts of Dindigul, Theni, Virudhunagar, Tenkasi & Tirunelveli likely to see heavy spells of rains in one or two places under the influence of temporary wind instabilities created by both the circulations. Similarly a few places in West TN also may come under heavy spell of rains. North TN including Chennai is likely to be under dry conditions today as well.