Withdrawal Watch:

The SW Monsoon officially began withdrawing from parts of West Rajasthan on 19 September. 

(IMD uses 5 consecutive dry days, establishment of an anticyclone at 850 hpa and below, and a marked reduction in atmospheric moisture as key criteria for the initial withdrawal.)

A new Bay ( BB-9) System deserves attention. 

Tracking Watch Alert: Vagaries opines that the withdrawing Monsoon Anticyclone and dry air can move and track the system NNW towards East M.P. and adjoining Bihar.

This Low, as it develops, is  important for Maharashtra. We will now observe if it shows westward progression and whether it slows withdrawal or feeds moisture back toward central/western India.. 

2. Mumbai — Synopsis:

As the Southwest Monsoon of 2026 enters its withdrawal phase, an interesting contrast has emerged between Mumbai and the country as a whole.

Mumbai — A Wet Monsoon....Mumbai has already crossed its normal seasonal rainfall..

{But a deficient India.}

Mumbai's above-normal seasonal rainfall should not necessarily be interpreted as a uniformly wet four-month monsoon. During just 1st–9th July, Mumbai received around 1,146 mm of rain. This extraordinarily concentrated spell contributed substantially to the seasonal surplus.

There were prolonged quieter periods between the major spells.

Outlook:

On 20th September, Colaba was 32.7°C / 25.1°C and Santacruz 32.3°C / 26.5°C; both recorded nil rainfall. The maxima were about +2°C.

Does the dry/warm phase persist, or do withdrawal-type thunderstorms return? 

Mumbai may still experience withdrawal-type thunderstorms during the latter part of September and into early October.

Withdrawal type Thunderstorms will commence from the 22nd.• Afternoon/evening thunderstorms associated with the seasonal transition. 

Mumbai can expect "Pop Up Thunderstorms" throughout this week 21st -25th in many parts of city.

Pune — A Different synopsis

Pune's rainfall distribution was distinctly different from Mumbai's coastal pattern.

July brought some exceptionally wet spells, but subsequent periods were comparatively subdued.

The Mumbai–Pune contrast once again illustrates how dramatically rainfall can change across the Konkan–Western Ghats–Deccan plateau transition.

Pune Outlook; Watch daytime heating. Pune is cloudy at about 32°C with 78% humidity. 

Lets expect if the clearer warm intervals allow maximum temperatures to rise sufficiently for late-day convectional Thunderstorms.

Interior Maharashtra :Madhya Maharashtra, Marathwada and Vidarbha can expect Thundershowers this week .

Maharashtra — Watch the Withdrawal Transition

The important question now is: Maharashtra moving towards withdrawal?

For Vagaries, the important indicators to monitor this week are:

• Sustained reduction in rainfall • Falling humidity • Changes in lower-level winds

• Development and position of the seasonal anticyclone • Withdrawal-line progression