After crossing the South Odisha coast at midnight on Thursday, cyclone ‘Daye’ has weakened into a deep depression and is on course to weaken further as a depression.
The deep depression lay close to Raipur (Chhattisgarh) and about 240 km east of Nagpur (Vidarbha) on Friday evening as it prepared to enter the rest of Central and North-West India.
The 24 hours ending Friday morning saw heavy to extremely heavy rainfall (20 cm or more in 24 hrs) over Odisha with heavy to very heavy rainfall over North Andhra Pradesh and Chhattisgarh.
The deep depression is set to cause heavy to very heavy rainfall over Chhattisgarh and East Madhya Pradesh until Saturday and over Vidarbha on both Saturday and Sunday.
Heavy to very heavy rainfall is also forecast over North Konkan, North Madhya Maharashtra, West Madhya Pradesh, East Rajasthan and East Gujarat Saturday.
Meanwhile, a remnant of the deep depression (a low-pressure area) is seen as interacting with an itinerant western disturbance over North-West India, and trigger heavy rainfall from Sunday.
Heavy rain has been forecast for Haryana, Chandigarh, Delhi, Punjab, Himachal Pradesh, West Uttar Pradesh and Uttarakhand on Saturday.
Sunday and Monday should see rains scale up over these regions with isolated heavy to very heavy rainfall. Isolated extremely heavy rainfall is also likely over Himachal Pradesh and Uttarakhand.
Monsoon withdrawal
An extended forecast by the IMD, valid from September 26 to 28, said that fairly widespread to widespread rain would occur over North-East India, while it would be scattered to fairly widespread rainfall over the South Peninsula and East India.
Isolated rainfall likely over the rest of the country except over parts of Northwest India where dry weather is likely to prevail as the withdrawal of the monsoon resumes from West Rajasthan.
The rain over the South Peninsula will be the handiwork of south-westerly monsoon winds over the Arabian Sea becoming north-westerly to northerly as an anticyclone starts to build in the sea.
The anticyclone with clockwise winds suppresses the formation of clouds and effectively signals the end of the monsoon flows from the south-westerly direction and across the Equator.
In fact, the monsoon trough should start moving to the Southern Hemisphere, with the withdrawal of the monsoon over land (North-West, East and Central India) taking place in tandem.
In the process, some rains are expected to happen over disparate areas over land due mainly from localised wind pattern and convection.
More rain ahead
For instance, in the South Peninsula, the winds from the building anticyclone in the Arabian Sea are forecast to blow around the peninsular tip into the Bay of Bengal. Some of the flows will head from the Bay into Tamil Nadu and Kerala and form a loop forming a rain-friendly cyclonic circulation.
An IMD wind field forecast suggests that these would unsettle the lower atmosphere over the South Peninsula and trigger thundershowers.
According to the US National Centres of Environment Prediction, these rains are expected to concentrate to the south-western coast and adjoining interior from September 29 to October 7.
Konkan, Goa, Coastal Karnataka, Rayalaseema, Interior Tamil Nadu and most of Kerala are expected to benefit from these end-September and early-October rains.
Meanwhile, with less than 10 days to go for the end of the 2018 South-West monsoon (September 30 is the threshold), the all-India rain deficit remains at 10 per cent.
The deficits are concentrated in the North-West, East, North-East and the South Peninsula with Lakshadweep (-46 per cent) and Rayalaseema (-35 per cent) the worst affected.