Last couple of days have seen an uptick of Veppa Salanam thunderstorms over Tamil Nadu with intensity picking up as well. While southern suburbs of Chennai recorded heavy rains on Tuesday evening yesterday saw some moderate thunderstorms in places around Maduranthagam / Chengalpattu region. The up tick in Veppa Salanam thunderstorms have coincided with the parking of Monsoon trough closer to the foot hills of Himalayas.
The trough is held firm along the hills by the quasi stationary Low Pressure Area over the Eastern Uttar Pradesh region for the past couple of days. With parts of UP & Bihar already reeling under heavy flooding there is no immediate respite likely for the region from heavy rains as more rains are expected over the next couple of days or so. Weather Models indicate conditions are conducive for Veppa Salanam thunderstorms today over many parts of Tamil Nadu.
While there exists a upper level wind instability in the convergence of different air masses over interior parts of Peninsular India the weakening monsoon surge is showing strong lower level convergence over the coastal areas of the state aided by strong sea breeze front that is expected to climb in altitude as well. Interior districts in the Western TN & Northwest TN around Salem, Erode, Namakkal, Vellore & Krishnagiri dts along with parts of South TN around Madurai, Virudhunagar, Pudukottai & Sivagangai could see isolated thunderstorms late afternoon.
Satellite images suggest a fairly clear morning ahead for most parts of Peninsular India which is likely to provide perfect radiation for convective storms to develop during the course of the day. When these interior storms interact with the sea breeze along the coast few places in the coastal areas are likely to see heavy thunderstorms during evening. Looking at wind charts the stretch between Puducherry & Chennai looks perfectly placed to benefit from these intensified thunderstorms. But before the thunderstorms set in we will have to bear another hot day across the state with many places recording Max temperature around 37 / 38°C.