The Upper Air Cyclonic Circulation near Andaman has now given way to a Trough of Low in Bay around the same region. Trough of Low is when the disturbance is loosely organized and shows a possible broad circulation over a larger area. In the meanwhile Adirampattinam in Thanjavur district has got 15 mm rains till morning today the only place to have got moderate rains in the Delta Districts.
Trough of Low in Bay Update:
The trough of low in Bay continues to struggle to create some sort of organization. It is pretty much a broad circulation now and expected to move in a Westward direction towards the Sri Lankan coast as things stand. The circulation is expected to come closer to the Sri Lankan coast around Monday from when the rains could pick up over Coastal Tamil Nadu. From this point models continue to have divergence on the likely events.
Ignoring the model divergence what looks fairly clear is there is likely to be an interaction with Sri Lankan landmass in all probability. This interaction with Sri Lankan landmass is going to be the game changer in terms of the rainfall pattern over Coastal Tamil Nadu both in terms of Intensity & Duration. Both GFS and ECMWF expects the weak circulation to survive this land interaction and continue its journey.
ECMWF expecting a NW track initially and the a NE recurve possibly under the influence of the Ridge to the east and then subsequently taking a SW track once again. GFS on the other hand expects a weak circulation to linger around Sri Lankan Coast / Tamil Nadu coast for days together and finally move into Arabian Sea around end of next week. Keeping in mind the current struggles the system is going through and a possible interaction with Sri Lankan landmass both the above scenarios are likely to be far fetched as of today.
Rainfall Update (Valid Till 1st December 2015) : Nevertheless there are few things which are likely to happen over the next few days, the rains are likely to return to Coastal Tamil Nadu from tonight possibly though during the day few isolated areas could get rains in the Delta region. From tomorrow we could see one or two places get heavy rains over the Delta region with Monday & Tuesday possibly seeing fairly wide spread rains over most parts of Coastal Tamil Nadu. As things stand it is going to be the Delta region which is possibly going to see heavy rains with possibly the stretch between Pondy & Rameswaram going to bear the brunt of heavy rains. During this period we could see possibly some heavy rains push into all the way up to Dindigul in South TN. Based on today’s inference we could possibly see the Areas to the South of Pondicherry get more rains than to the North of Pondicherry.
Chennai Rainfall Update (Valid till 1st December 2015). While during the day Chennai could see possibly clear weather, some isolated rains might be possible tonight. From tomorrow we could see more spells of rains with possibly the rains increasing in intensity from Monday. As things stand the heaviest spell of rains for Chennai possibly awaits around Monday midnight / Tuesday morning