India Meteorological Department (IMD) has withdrawn the watch for a low-pressure area that it was expecting over the North Bay of Bengal after an upstream circulation in the Arabian Sea and heat wave conditions in Rajasthan saw the ruling weather conditions being rearranged overnight on Thursday.

Wind maps showed the rogue circulation in the North Arabian Sea pulling back a bulk of the incoming monsoon flows to itself (though the rest fanned into Mumbai, dropping moderate to heavy rain) while opportunistic dry north-westerlies from Rajasthan filled East India, weakening an existing monsoon circulation.

This circulation has been the pivot around which the monsoon was holding out over East and adjoining Central India. Weakening of the circulation has also led to the collapse of a crucial shear zone of turbulence in the higher levels of the atmosphere, probably indicating how the progress of monsoon has been stalled.

Regional pivot lost

Still a semblance of order is being maintained thanks to the presence of another circulation in the immediate neighbourhood and located over Jharkhand. Also present is a land-based trough that runs from the North-West to South-East extending from as far away as Central Pakistan right into Manipur in North-East India, the IMD said.

They would help keep the monsoon busy but confined to East and North-East India for the next five days. Widespread rainfall with isolated heavy to very heavy fall is likely over this region during this period. The IMD saw isolated extremely heavy rain over the hills of West Bengal, Sikkim and Meghalaya on Thursday itself.

Central India too may experience fairly widespread to widespread rainfall with isolated heavy to very heavy falls across East Madhya Pradesh and Chhattisgarh during the next five days. Light isolated to scattered rain or thundershowers are forecast over North-West India except Uttarakhand where a western disturbance would bring fairly widespread rainfall with isolated heavy falls.

May build crucial mass

The European Centre for Medium-Range Weather Forecasts as well as the IMD expect the circulation over Jharkhand to build some mass from an extended stay over the region and getting a move gradually to the West-North-West even in the face onslaught from dry westerlies from the Thar.

It would also bring moderate showers around a core of heavier rain first to Central India, before taking it to West India and parts of South-West Rajasthan (light or spotty showers) over the next 9-10 days. The IMD seems to concur, suggesting no significant rain for the desert state at least until June 28.

Along with East and North-East India, parts of the East Coast – especially Coastal Andhra Pradesh, Tamil Nadu and Puducherry - are forecast to receive rains during the intervening period. This is a pattern observed when the South-West monsoon is not doing exactly well over large parts of the rest of the country.

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