Monsoon-friendly easterly winds are getting replaced by dry and warmer westerlies to north-westerlies over the Indo-Gangetic plains, says the Noida-based National Centre for Medium-Range Weather Forecasting (NCMRWF).
This has coincided with the northward shift of the monsoon trough to the foothills of the Himalayas from Thursday, the NCMRWF said in its bulletin on Friday.
The trough would stay pinned to the alignment along the foothills until at least Monday, subsequent to which it would start moving back to the south.
CYCLONIC CIRCULATION
This is expected to happen under the influence of the formation of a land-based cyclonic circulation over Bihar and adjoining region around Wednesday.
There is still no sign of a low-pressure area taking shape near the head Bay of Bengal that alone could drag the trough further east-southeast to anchor it along the most ideal alignment for monsoon to revive in the northern plains.
Meanwhile, the ongoing weak phase of the monsoon is paradoxically seen bringing the long-delayed rains over Uttar Pradesh and Bihar.
The significant rain deficit in east India as on Thursday (in percentage figures) was: east Uttar Pradesh –69; Jharkhand – 51; Bihar – 43; east Madhya Pradesh – 39; and west Uttar Pradesh – 36.
Most of these areas are forecast to receive moderate to heavy to very heavy rainfall during the next few days as the monsoon trough sits in close proximity.
RAIN COVER
The NCMRWF cited model predictions that favoured increase in rainfall along the foothills and adjoining Uttar Pradesh, Uttarakhand, Bihar, Sikkim and the Northeastern States during the next three to four days and subsequently over the eastern States (West Bengal, Chhattisgarh, Jharkhand, Orissa and eastern Madhya Pradesh).
The rainfall along the west coast also is likely to continue, especially in the Konkan-Goa belt. On Friday, the offshore trough continued to run from Gujarat coast to Kerala coast, an update by India Meteorological Department (IMD) said.
International models indicated the likelihood of a wave of rains from east India (likely let loose by the land-based cyclonic circulation) docking itself with a counterpart wave from the west coast over central India soaking the land west to east. As for the west coast, a similar convergence with convection emerging from west equatorial Indian Ocean (around Maldives) is also likely, helping spread the rains all along the coast from time to time.
CONVECTION ANOMALY
Meteorologists see the ongoing convection over west equatorial Indian Ocean largely responsible for weakening the monsoon current that turn west and then northeast into the Arabian Sea.
A warning valid for the next two days issued by the IMD said that isolated heavy rainfall would occur over Konkan, Goa, coastal Karnataka and Kerala.
Isolated heavy to very heavy rainfall has been forecast over Arunachal Pradesh, Assam, Meghalaya, sub-Himalayan West Bengal, Sikkim and Bihar.
Scattered rain or thundershowers have been forecast for Chhattisgarh, Jharkhand, Orissa, Gangetic West Bengal during the next two days with the possibility of scaling up further in intensity.
A separate warning for east Uttar Pradesh said that isolated heavy rain is likely to commence over east Uttar Pradesh from Saturday.
As for central India, the IMD has forecast scattered rain or thundershowers for Gujarat, Madhya Maharashtra, Madhya Pradesh, Vidarbha, coastal Andhra Pradesh, Telangana and interior Karnataka.
An intervening western disturbance is expected to bring scattered rain or thundershowers over Punjab, Haryana, Chandigarh, Delhi, Himachal Pradesh, and Uttarakhand over the next two days.
Extended forecast until Wednesday (July 14) indicated the possibility of a decrease in rainfall over central and peninsular India.
But widespread rainfall with isolated heavy to very heavy falls would continue over east Uttar Pradesh, Bihar, sub-Himalayan west Bengal, Sikkim and the north-eastern States.
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