Thiruvananthapuram, June 27
The build-up along the Arabian Sea and the west coast is peaking ahead of fresh spurt in monsoon flows over the Arabian Sea and heavy rains along the peninsular coasts.
The west coast and, to a lesser extent, the eastern coast are expected to witness heavy to very heavy rainfall from around July 1 (Thursday), according to consensus forecasts by forecasting agencies.
An India Meteorological Department (IMD) update said on Sunday that an offshore trough extending from south Gujarat coast to coastal Karnataka coast has been lying in wait to receive the enhanced flows.
Fairly widespread rain or thundershowers are likely to occur over Konkan, Goa, coastal Karnataka and Kerala during the next two days before scaling up further, the IMD said.
In a warning valid for the next two days, the IMD said isolated heavy rainfall is likely over Konkan, Goa and coastal Karnataka.
Isolated heavy to very heavy rainfall has also been forecast over West Bengal, Sikkim, Arunachal Pradesh, Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura.
Forecast until Friday said that the fairly widespread rainfall would continue over east and northeast India and along the west coast.
Isolated heavy falls are forecast to continue over the west coast, the Northeastern States and adjoining east India.
Leading international models also concurred with the outlook for enhanced rainfall for the peninsular coasts as well as for east-central and northeast India as well as the east coast northeast-ward from south coastal Andhra Pradesh.
The US National Centres for Environmental Prediction (NCEP) is of the view that east-central Arabian Sea and the contiguous west coast of India, east-central and east India would slip under a wet cover during the ongoing week ending July 4 (Sunday next).
Its outlook for the following week (July 5-13) shows the entire eastern quadrant of the country witnessing good rainfall.
However, the monsoon would still not have covered central, eastern and northern parts of Rajasthan, the last State to be covered in the onset phase.
The NCEP indicated that parts of northwest Madhya Pradesh adjoining east Rajasthan too would be kept waiting for the rains, due largely to suspected rogue northwesterly flows.
Global Forecasting System (GFS) model of the Climate Prediction System of the US National Weather Services also views evolving weather over northwest India along these lines.
WAIT FOR RAJASTHAN
Its forecast for the week ending July 11 says that central and northwest Rajasthan could sit out even as surrounding areas receive monsoon rains. The IMD has already gone on record in its forecast bulletin saying that a feeble western disturbance would be in action over northwest India for the next three days.
While this could help set up cloudiness and rainfall over parts of the region after running into monsoon easterlies, it could also prevent the latter from penetrating the region and establish monsoon.
However, the long-range outlook for the entire northwest region continues to be above-normal rainfall during the four-month season from June.
Satellite cloud imagery on Sunday showed convective (rain-producing) clouds over parts of Orissa, sub-Himalayan West Bengal, Sikkim, the Northeastern States, Chhattisgarh, Vidarbha and east-central Arabian Sea.
Forecast valid until Wednesday said that widespread rain or thundershowers would occur over the Northeastern States and adjoining sub-Himalayan West Bengal and Sikkim. Scattered rain or thundershowers are expected over Gangetic West Bengal, Orissa, Jharkhand, Bihar, Madhya Pradesh, Madhya Maharashtra, Vidarbha, interior Karnataka and Chhattisgarh.
Isolated rain or thunderstorms would occur over western Himalayan region, Punjab, Haryana, Chandigarh, Delhi, Rajasthan, Uttar Pradesh, Marathwada and Andhra Pradesh.
An outlook from the Regional Met Centre, Chennai, for the next two days said that rain or thundershowers may occur at many places over coastal and south interior Karnataka and Kerala and at a few places over North Interior Karnataka and Lakshadweep.
Isolated rain or thundershower may occur over Tamil Nadu, Puducherry and Andhra Pradesh. A warning valid for the period spoke about the possibility of isolated heavy rain over coastal Karnataka, the ghat areas of south interior Karnataka and Kerala.