Reasoning for rains – Whenever an upper Air Circulation (UAC) forms in south west monsoon (June-September) in South West bay off Tamil Nadu coast, it creates lots of convergence in the interior part of Tamil Nadu. Still the heat will be the trigger point for rains. However, the storms formed will have good synoptic support in the form of UAC and lasts longer.
With winds from east, the storms forming in the interiors will struggle to move into the coastal areas. So movement or steering of storms will be slow and stand and deliver rains will be seen in some locations.
Today – Districts like Dindigul, Tiruppur, Krishnagiri, Dharmapuri, Tirupattur, Thirvannamalai, Vellore, Salem, Namakkal, Trichy, Perambalur, Ariyalur, Kallakurichi, Villupuram, Karur, Madurai, Coimbatore, Nilgiris ,Erode and many other interiors will be in hotspot for rains. South TN areas like nellai, thenkasi, theni, virudhunagar will also get rains.
Chennai – Delta got good rains in morning as it fell in southern side of the circulation. For Chennai outskirts will see some action and morning some puffy clouds will seen. For Chennai widespread rains, it needs to wait till 24/25 when UAC fades away and westerlies return.