Dharmapuri and Krishnagiri districts in Northwest Tamil Nadu share a lot in common with the adjoining areas of AP & Karnataka. It is no wonder this trijunction of modern states were called Morasunadu. One another common fabric that binds these areas in addition to culture is weather. Like Bengaluru the rainiest months coincide with the transition seasons for these two districts. Three months, April, September and October bring more than half of the annual rainfall for these two districts. Similarly some areas of Tirupattur, Tiruvannamalai that abut these districts also share the same traits. Just like Bengaluru this year rains during September was poor over the Northwest Tamil Nadu districts as well.
The good news though is as transition dynamics start these areas could be the biggest beneficiaries of the upcoming rains. The last few days saw parts of South TN and West TN record very good rains due to temporary Easterlies. The cyclonic circulation that brought this phase of Easterlies has now shifted further west. This in turn will now bring back Westerlies triggering one last phase of thunderstorms from the west. Over the next couple of days convergence created by the returning Westerlies will trigger storms over interior areas.
As we get to the weekend an East West Shear zone is likely to develop over South Central Bay. This will set the stage for widespread thunderstorms. Over the course of next week to 10 days most places in Northwest Tamil Nadu can get some much needed rains. In addition to these districts adjoining areas of Karnataka and AP is also likely to see good rains. Places like Bengaluru can look forward to a sustaining spell of thunderstorm activity until middle of October. With favourable winds few places may see as high as 15 to 20 cms of rainfall accumulation before Monday.
Coastal areas are also likely to get good rains though the biggest beneficiary is expected to be NW Interior TN. As withdrawal of Southwest Monsoon picks up pace there will be a period when interior areas will outscore coastal areas. But overall first fortnight looks good for most of Tamil Nadu to receive good rains. From the weekend until possibly middle of next week coastal and areas like Chennai and also Delta may see moderate rains which will keep the seasonal tally going.
With the imminent arrival of MJO into Indian Ocean during the middle of October things are likely change favorable for NEM Onset. With the jigsaw pieces slowly falling in place another good Northeast Monsoon season is on the cards. A detailed post on what to expect from Northeast Monsoon 2024 will be put out in due course.