A post on the return of Summer over Tamil Nadu may surprise many at this time of the year. The last couple of days chatter among weather blogging community has been about NEM 2024. A fairly positive outlook from ECMWF Seasonal forecasts seem to have set the cat among the pigeons. With delayed transition to Nina it may not be a surprise if some of these forecasts flip during October. In this context it becomes essential to take couple of weeks at a time.
After a weak August September is also likely to see sub par rains over Peninsular India. As this daily rainfall chart indicates Kerala has seen a substantial reduction in rains since the late July surge. Sub seasonal models picked up this weak spell well though seasonal forecasts indicated above average rains for August. Kerala has been steadily seeing an increase in rains during the 2nd half of Monsoon. It appears 2024 may see a weak end to the monsoon season. South Kerala has a robust NEM season as well so hopefully that compensates to some extent.
The incidental impact of weaker monsoon dynamics over the west coast is increased temperatures over the East Coast. After many weeks on Thursday an IMD observatory in Tamil Nadu recorded 40°C with Madurai AP recording 40.8°C. Yesterday both City and AP observatories at Madurai crossed 40°C. Forecasts indicate for the next couple of weeks temperatures over Tamil Nadu may be 2 to 4°C above normal. In particular southern parts of the state is likely to be abnormally hot until end of next week. Models indicate third week of September may see large parts of the state remain abnormally hot with drier weather conditions. The Low Pressure Area over Bay is likely to move North gradually leading reduction of moisture over Peninsular India. This in turn will bring clearer skies and hotter afternoons.
As was the case of the depression that became Cyclonic Storm Asna this LPA is also likely to amble along slowly. This may potentially bring flooding risk to parts of Odisha, Chhattisgarh, East UP and East MP. With slower movement it may also lead to longer spell of dry weather over Peninsular India. Weaker monsoon means hotter afternoons for the plains of Tamil Nadu. Models are showing cooler than normal temperatures over Northwest India for the next couple of weeks. This confirms not only the slow movement but also a delayed start to withdrawal of SWM. The revised date of withdrawal for NW India is 17th September. This could potentially mean a delayed start to withdrawal is on the cards.
Reduced moisture availability will mean thunderstorm activity may be subdued over TN. Over the next few days parts of TN particularly along the coast may see moderate thunderstorm activity. Interior areas though may see dry weather persist with possibly transition season thunderstorms as the hope. With delay in the start of withdrawal transition thunderstorms may be pushed to early October over interior Peninsular India. Until then heat is the name of the as Tamil Nadu enjoys its 2nd summer.