Thiruvananthapuram, July 19 A fresh well-marked low-pressure area has parked itself over northwest Bay of Bengal with prospects of intensification into a monsoon depression.
Once again, east and central India have been brought under a renewed spell of rains but indications are that they would extend to west India, besides over the rain-scarce northwest India in stages.
RAIN GAINS The Global Forecasting System model of the US Navy’s Fleet Numerical Meteorology and Oceanography Centre (FNMOC) sees Uttar Pradesh and Bihar, among the worse hit from a long-drawn dry spell, making some gains.
According to this model, a stream of easterlies from the likely depression would fan west-northwest across central India to be redirected north-northeast towards Uttar Pradesh and later Bihar.
But the core of easterlies would head for central India and later into west-central India and the west coast, before the parent system slips into northeast Arabian Sea.
North Rajasthan, Punjab and Haryana - which combine to virtually make up the country’s granary - may manage to get only sparse rains since the ‘steering system’ around Rajasthan may divert the easterlies.
This steering would be provided by the quasi-subsidence motion of air, leading to a high-pressure regime (a ‘high’) and a rain-thwarting anti-cyclonic circulation in the region.
This is an extension of massive ‘blocking high’ extending from West Asia to Europe, which does just that – block western disturbances whose interaction with easterlies set up most monsoon rains over the northwest.
BREAK-MONSOON? The European Centre for Medium-Range Weather Forecasting has projected the arrival a westerly trough into east India around July 25 to coincide with the formation of the next ‘low’ over west-central Bay.
The eastward moving trough would appropriate the ‘low’ to itself and orient it towards a north-northeast direction - from the Andhra Pradesh coast towards Gangetic West Bengal by July 27, up to which forecasts were available.
This could bring widespread rainfall to Bihar and the north eastern States, according to the FNMOC forecasts but some meteorologists fear if this would not bring about a ‘break-monsoon’ condition also.
This is so since the ‘low’ could drag the crucially important seasonal monsoon trough with it and slot it to a perch along the foothills of the Himalayas.
A ‘break monsoon’ would mean switch-off of rains over central and northwest India except partly along the west coast, east India and the southeast coast.
But the latter two may benefit from long-overdue precipitation.
Meanwhile, an India Meteorological Department (IMD) update has warned of heavy to very heavy rainfall with isolated extremely heavy falls exceeding 25 cm at a few places over Orissa during the next two days.
HEAVY RAINS Isolated heavy to very heavy rainfall is also likely over Konkan, Goa, coastal Karnataka, Kerala, Chhattisgarh, north coastal Andhra Pradesh, Telangana, Vidarbha, east Madhya Pradesh and Bihar.
The three days that follow would see fairly widespread to widespread rainfall over the west coast, Gujarat, south Rajasthan, south Madhya Pradesh, north Maharashtra and the Andaman and Nicobar Islands. The Chennai Met Centre said in an update that the monsoon has been active over coastal and south interior Karnataka during the 24 hours ending Sunday morning.
Isolated rainfall occurred over Tamil Nadu, Rayalaseema and Telangana.
Forecast for the next two days said that rain or thundershowers are likely at most places over Kerala and coastal Karnataka and many places over interior Karnataka, north coastal Andhra Pradesh and Lakshadweep.
Thundershowers have been forecast for Telangana and south coastal Andhra Pradesh. Isolated rain or thundershowers are likely over Tamil Nadu, Puducherry and Rayalaseema.