The incoming rain-driving cyclonic circulation originating from South China Sea was spotted this (Monday) morning over Myanmar, a sniffing distance away from the North Bay of Bengal where it is expected to land any time, and set up the eagerly-awaited low pressure to escalate the monsoon over India.

Ahead of it, the all-important monsoon trough over the North has shifted as a whole to its normal position — the eastern end had till now stubbornly refused to take a cue from the western end to move southward — and lay extended on Monday morning from Ganganagar in West Rajasthan to Narnaul, Gwalior, Varanasi, Dehri, Jamshedpur, Balasore, and thence, eastwards to the North Bay of Bengal.

Ideal setting for monsoon

This is the most ideal setting for the monsoon trough; formation of a low-pressure area in the Bay is a pre-condition for its eastern end to behave. Active monsoon conditions are generated when the eastern end finds its moorings in the Bay while being anchored in the waters along with the low-pressure area.

This apart, the monsoon would also have the assured comfort from an East-West wind convergence zone along Kolhapur-Hyderabad-Visakhapatnam, providing the low-pressure area familiar turf (unstable air) to move around. The low would travel over Madhya Pradesh and Gujarat before sliding into North Arabian Sea.

The short-to-medium-range model guidance from the India Meteorological Department (IMD) suggests the formation of a successor low-pressure area in the Bay any time after August 8, and the seas there likely continuing to be in an animated state into the middle of August, sustaining active monsoon conditions.

Clouds massing up over Bay

In its outlook for the next three to four days, the IMD said the south-westerly monsoon flow is likely to strengthen over the Arabian Sea and along the West Coast due to emergence of the low-pressure area in the North Bay and consequent increase in North-South pressure gradient and strengthening of winds.

Satellite pictures on Monday mid-morning showed clouds having thinned over the Arabian Sea and massing up in huge size off the Tamil Nadu coast and into the Andaman Islands and over West-Central, West and adjoining North and North-East Bay, in relation to proximity with the incoming cyclonic circulation.

The monsoon will enter active phase over Central and Peninsular India from Tuesday and stay like that for the subsequent three-four days, the IMD said. Widespread rainfall with scattered heavy to very heavy rainfall with isolated extremely heavy falls is likely over Konkan and Goa till Wednesday.

Heavy rain for Mumbai

Over adjoining Mumbai, heavy to very heavy rainfall has been forecast for today (Monday), followed by isolated extremely heavy falls on Tuesday and Wednesday. The IMD indicated that a similar outlook is valid for Madhya Maharashtra, including the Ghat areas on Tuesday and Wednesday.

In the South, heavy to very heavy falls are likely over Coastal Karnataka, Kerala and Marathawada from Monday to Wednesday. In the West, widespread rainfall with heavy to very heavy rainfall with isolated extremely heavy falls is forecast over coastal Gujarat region on Wednesday and over Gujarat state on Thursday.