After a few days of good thunderstorm activity Convective Rains in Tamil Nadu is expected to slow down over most parts of the state in the coming days. The last few days once again confirms the link between increased Veppa Salanam Rains in Tamil Nadu when the Monsoon trough parks itself closer to the foot hills of Himalayas. On Monday while Chennai and surrounding areas recorded good rains the highlight was Samayapuram which recorded 17 cms rivaling some of the rainfall numbers recorded by west coast places during peak monsoon.
Yesterday as expected was a relatively dull day of thunderstorm activity with couple of thunderstorms forming around Vellore & Kallakurichi region while one extremely isolated thunderstorm happened close to Tambaram. Today we could see some activity around South TN & Delta districts though intense thunderstorms are unlikely. Numerical Models indicate parts of South TN to see slightly above normal temperatures which could influence convective activity. The weak monsoon conditions prevailing over southern parts of Peninsular India is seen in the temperature charts with West coast seeing hotter conditions. Places like Chennai could see near normal afternoon temperatures due to prevailing partly cloudy skies.
While a lot of talk normally happens around the role of sea breeze in triggering convective rains in Tamil Nadu one can never discount the fact that all of these episodes that involved intense thunderstorms had wind instabilities at atmospheric / Mid Tropospheric levels. The current episode also had similar conditions with Mid Tropospoheric instability prevailing during this period in addition to complete slowing down of Westerlies at lower levels allowing not only to sea breeze to penetrate inland but also climb up the latitude too.
With westerlies streamlining in anticipation of improving monsoon dynamics we can start seeing some of these instabilities fade away reducing the chance of thunderstorms over most parts of the state.