While majority of India looks forward to the onset of Southwest Monsoon eagerly during late May the withdrawal of Southwest Monsoon is eagerly looked forward too by a few. As most know the withdrawal of Southwest Monsoon kick starts the change towards Northeast Monsoon the primary monsoon for Tamil Nadu & parts of Coastal Andhra Pradesh along with parts of Kerala & Karnataka which receive good rains too.
The thunderstorms that has been rocking the interior parts of Peninsular India is an indication of the atmosphere getting ready for Monsoon withdrawal. As we keep repeating often thunderstorms happen when the steering winds are weak be it Westerlies or Easterlies. The current phase of thunderstorms coincides with weak Westerlies making the atmospheric conditions conducive.
Today once again pseudo LWD Conditions is running all the way from Interior Karnataka / Rayalaseema to Central Tamil Nadu which is likely to trigger heavy thunderstorms in a few areas along the line. Yesterday saw parts of Bengaluru record heavy spells of rains for second straight day and it appears today once again areas around the Southern periphery of the metropolis bringing the risk of localized water logging once again. The interior districts of Tamil Nadu is also likely to see isolated heavy spells of thunderstorms later in the evening / night.
IMD has Cessation of Rainfall for 5 continuous days, Reduction in Moisture and the establishment of Anti Cyclone in the lower troposphere as the criteria for withdrawal of Southwest Monsoon from Northwest India. After the influence of remnant Cyclone Daye faded away the rains have reduced in Rajasthan from the late hours of 23rd. Numerical Models indicate the establishment of a weak anti cyclone at 850 hPa levels around 28th / 29th September. By this time possibly we would have seen 5 continuous days of no rainfall activity over most parts of Rajasthan confirming the withdrawal of Southwest Monsoon.
From then slowly curtains will be drawn for Southwest Monsoon 2018 bringing an air of expectation among Chennai Weather Bloggers towards Northeast Monsoon 2018