If Sunday saw Tamil Nadu record its highest weighted average for the state this season Monday went up a notch higher as Interior Tamil Nadu saw thunderstorms light up the skies across the state with some heavy duty rains over districts like Vellore, Tiruvannamalai, Dharmapuri and the delta districts. Not to be left out even Thootukudi district which has so far propped up the Monsoon Rainfall table with the poorest rainfall statistics in SWM 2017 across Tamil Nadu saw intense thunderstorms strike a few parts of the district.
The TN agri University Weather station at Kandhili, about 15 kms to the west of Tirupathur, recorded more than 10 cms rains for the day while not far away the IMD weather station at Vaniyambadi recorded 75 mm till 4:30 in the morning. Both Tiruvannamalai & Vellore district continued to get rains almost right through the night in many places.
Earlier in the day it was the turn of Delta districts & South TN to enjoy these sound and light show in the skies as places like Thanjavur, Mannargudi, Ammapettai, Kovilpatti recorded rain rates of about 4 to 5 cms an hour as skies opened up in these places.
One of the key factors of these rains for the last couple of days have been the pattern of late night thunderstorms which is typically associated around September. The last couple of days and to some extent even today there is a pseudo wind discontinuity that is prevailing over the southern parts of Peninsular India which has created these explosive conditions for the thunderstorms to thrive upon. This Mid Tropospheric trigger is also the reason why the storms have thrived for long and widespread.
Typically around September end when the monsoon dynamics change from the Westerly to Easterly regime one starts to see such wind Discontinuities develop along parts of Peninsular India bringing in heavy rains associated with heavy thunderstorms.
Things look good for rains to continue in parts of Tamil Nadu with places in South TN and interiors scoring heavily, but things are expected to slow down overall for a couple of days before things once again pick up after 4th / 5th of August.