Rain burst likely before monsoon withdrawal
IMD scientists are expecting the withdrawal of monsoon to commence from west Rajasthan only after September 25; the four-month monsoon will come to an end on September 30, and any rain recorded after that will be counted as post-monsoon rain.Updated: Sep 22, 2020, 00:56 IST
Parts of India are likely to experience a late burst of rainfall in the next two to three days when the monsoon normally begins its gradual withdrawal. A low-pressure area over northwest India is likely to bring widespread and heavy rains to the west coast, the east and the peninsular region, India Meteorological Department (IMD) scientists said on Monday.
IMD scientists are expecting the withdrawal of monsoon to commence from west Rajasthan only after September 25; the four-month monsoon will come to an end on September 30, and any rain recorded after that will be counted as post-monsoon rain. As of Monday, the monsoon is 7% excess this year, although there are significant variations across regions. It is 29% excess over the southern peninsula, 14% excess over central India, 1% excess over northeast India, but 16% deficient over northwest India. Since a plus/minus 19% deviation from the long period average is counted as normal, this means rainfall is normal in three of the regions, and above normal in the fourth.
Following intense showers in the west, east and even several parts of Uttar Pradesh, IMD is expecting reduced rainfall over the country, which may make conditions favourable for commencement of monsoon withdrawal from northwest India.
The low pressure system will move west-north-westwards up to central Madhya Pradesh and then recurve towards Uttar Pradesh. We are expecting very good rains in UP too during this spell,” said RK Jenamani, senior scientist at the National Weather Forecasting Centre.
The low pressure area is lying over northwest Bay of Bengal and adjoining north coastal Odisha.
“We are expecting rains to reduce significantly once this low pressure system passes. There is no likelihood of another low pressure area forming in the next seven days,” said M Mohapatra, director general, IMD.
The normal date for commencement of monsoon withdrawal from northwest India is September 17 and for complete withdrawal from the country, October 15. The new monsoon onset and withdrawal dates were issued by IMD in April. Until last year, the normal date for commencement of withdrawal was September 1 and for complete withdrawal was October 15 .
IMD’s new onset dates are based on an analysis of monsoon data from 1961 to 2019 and withdrawal dates are based on data from 1971 to 2019 by scientists in IMD, Pune.
“We are not seeing any parameters of monsoon withdrawal being met in the next two days. Rain should stop completely but it rained in west Rajasthan on Saturday and there is water vapour in the region; anti-cyclonic wind pattern is also not established yet. We have to monitor if conditions are becoming favourable for withdrawal after the low-pressure area weakens. But the monsoon season will end on September 30. There are no changes to the season,” said K Sathi Devi, head of the National Weather Forecasting Centre.
Last year, the monsoon started withdrawing only on October 9 against the normal date of September 1 and withdrew completely only by October 17.