It is often said sea breeze is the savior for Chennai modulating our day time temperatures towards the evening and bringing a waft of humidity through the city. The common public may not realize one other role sea breeze plays in bringing another key weather event to Chennai, Rains associated with thunderstorms, particularly during Southwest Monsoon period. Not only the absence of sea breeze makes it an uncomfortable evening for Chennaites during the summers but the absence of sea breeze also reduces the chance of thunderstorms as well.
When Monsoon is active the westerlies remain strong thereby eliminating the arrival of sea breeze on most days. In particular when there is a cyclonic circulation in Head Bay (North Bay) there is next to zero chance for sea breeze to show up over the Chennai coast even though due to its peculiar convex coastline typically Chennai enjoys better sea breeze than most of its counterparts along the East Coast.
With the Well Marked Low now over parts of Madhya Pradesh and adjoining areas we can see some bit of weakening of westerlies over southern parts of Peninsular India. Unlike active monsoon conditions across the country currently it is Cental India & NW India that is enjoying the favorable conditions providing a window of opportunity for coastal areas to catch up a spell or two of sea breeze induced thunderstorms.
With possible wind convergence along with weak winds from the west between 1.5 to 3 kms ASL altitudes interior places about 100 to 125 kms from the coast line could see some thunderstorm development later in the afternoon which will move towards the coast later in the evening. Weather models indicate coastal areas to come under a fairly strong sea breeze front which could then interact with the remnant moisture coming from the West triggering thunderstorms along the TN Coast.
The stretch between Chennai & Pondicherry looks ideally placed for thunderstorms with one or two places in this stretch in line to catch up an intense spell of rains. With some favorable wind pattern there is a chance the southern suburbs of Chennai could sneak in one or two heavy spell of rains