Last night finally saw what could be called perfect Northeast Monsoon onset conditions as parts of Delta districts came under moderate to heavy spell of rains. The IMD observatories at Karaikal & Nagappattinam recorded 8 & 10 cms of rains respectively up to 5:30 AM. Chennai & suburbs also witnessed some intense thunderstorms in a few places with light to moderate rains recorded in central & northern parts of the city. Interestingly the storms started to intensify as they crossed the city areas with western suburbs of Chennai recording more rains rather than places along the coast line.
Typical of Northeast Monsoon as this post is being typed bright sunshine is seen at Chennai indicative of how the rains happen most of the time before most people wake up during NEM time. All you get to hear is there are no rains only bright sunshine. The regular NEM day goes like this Coastal Areas see an uptick in rains once sun goes down with the peak seen between 12 AM & 6 AM. As the sun rises the remnant moisture that gets pushed inland starts interacting with the increasing day time temperatures over interiors to trigger rains accompanied by thunderstorms in the interior places during the day time.
Satellite image indicates the strengthening impact of Easterlies as South Bay is seen with good convection influenced by the LPA off the coast of Sri Lanka which is stationed at a favorable location to give fairly widespread rains over Tamil Nadu for the next couple of days. This could keep the current spell of rains going until early next week with mostly moderate rains seen with few places coming under heavy spell of rains depending on localized condition & convection movement.
The LPA is expected to slowly move westward for the next 48 hours or so giving a good window of rains for Delta districts & South TN which might see heavy rains in a few places today & tomorrow. In the meanwhile Chennai which saw rains during the early morning hours may see sunshine interspersed with occasional spell of rains during the day time, later in the night / early morning hours rains will pick up once again to bring moderate rains across the city with one or two places getting heavy rains.