Below Par SW Monsoon in TN running out of time

The official Southwest Monsoon season over the Indian sub continent is now entering into the final week.  With just 8 days left in September 2018 is turning out to be a season of early promise fading away.  According to the official weather agency of the country, Indian Meteorological Department, the Southwest Monsoon officially ends on 30th September irrespective of the withdrawal status of the Monsoon.

From the statistics point of view to compare long term trends it makes sense to follow a fixed date though purists could argue rainfall numbers should be based on actual monsoon status. The current score card for the country as a whole is at -9.8% just below the threshold of a deficit monsoon.  With thunderstorms the only hope in the remaining days a drastic improvement on this number looks less likely.

Cyclone Daye which crossed South Odisha coast yesterday early morning has now weakened into a depression and currently lies over Maharashtra and adjoining parts of Madhya Pradesh.  This system is expected to further weaken today and slowly fade in its influence.  Before it completes its life cycle it is expected to give moderate to heavy rains in many places of Maharastra, Madhya Pradesh and parts of Gujarat & Rajasthan.

As many know Tamil Nadu being a relatively rain shadow state during Southwest Monsoon owes most of its rains to thunderstorms rather than proper Monsoon rains.  Just like how monsoon performed in bits and parts across the country even in Tamil Nadu it has been very erratic this year and is highlighted by the current status of -15% deficit as of yesterday for Tamil Nadu & Puducherry sub division.  The good news though with thunderstorm activity expected to pick up during the last week of monsoon season we could see some improvement in this number but overall we are unlikely to touch the seasonal average and will possibly end with about 10% deficit for the season.

With clearer skies expected over parts of South India, convective activity is expected to pick up. Models indicate some wind instabilities around Central & South TN today to trigger moderate thunderstorm activity.