Monsoon withdrawal likely from Sept 25: IMD
While there is a 6% deficiency in seasonal rainfall, the shortfall is 19% over east & northeast India; 1% over central India, & 10% over peninsular India.
New Delhi: The monsoon will begin withdrawing from west Rajasthan around September 25, roughly 8 days later than when it usually begins receding, officials said on Friday, adding that a recent surge in rains has cut a 10% deficiency in precipitation at the end of August to 6% on Friday.
But that gap is unlikely to change much and rains are now expected to reduce over northwest and adjoining west central India over the next 5 days, the India Meteorological Department said, describing the conditions as “favourable for withdrawal of southwest monsoon from parts of West Rajasthan from around September 25”. The normal date for monsoon withdrawal to begin is September 17 and completely withdraw by October 15. The monsoon season officially ends on September 30.
While there is a 6% deficiency in seasonal rainfall, the shortfall is 19% over east and northeast India; 1% over central India, and 10% over peninsular India. There is a 2% excess over northwest India.
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Rainfall of 90 to 95% of LPA is considered to be in the “below normal” category while less than 90% is considered “deficient.” Monsoon rainfall between 96 to 104% is considered “normal.”
Heavy to very heavy rain however is likely to continue over Bihar, Jharkhand, sub-Himalayan West Bengal, Sikkim and over northeast India on September 22 and 23. Thunderstorms accompanied with lightning are likely over Madhya Pradesh, Vidarbha and Chhattisgarh on Friday.
“Due to anti-cyclonic flow developing over northwest India at lower tropospheric levels and dry weather prevailing over parts of southwest Rajasthan, conditions are becoming favourable for withdrawal of southwest monsoon from parts of West Rajasthan from around September 25,” IMD said in its bulletin.
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The low pressure area over Jharkhand and neighbourhood has become less marked. However, the associated cyclonic circulation is lying over west Jharkhand and neighbourhood in middle tropospheric levels. Another trough is running from Sikkim to south Madhya Maharashtra across Bihar, cyclonic circulation over west Jharkhand, Chhattisgarh, East Madhya Pradesh, Marathwada in lower and middle tropospheric levels. A cyclonic circulation is lying over south Pakistan and adjoining Kutch and another over south Tamil Nadu in middle tropospheric levels.
“Monsoon has revived in September. Though August was very badly impacted by El Nino and we had a 10% deficiency, there was very good rainfall in September and this helped agriculture. This also shows that the Indian Summer Monsoon is influenced by several factors, not just El Nino Southern Oscillation (ENSO). In September, the position of Madden–Julian oscillation is favourable and the Indian Ocean Dipole is positive. These may have helped the monsoon revive,” said M Mohapatra, director general, IMD. MJO is described as an eastward moving pulse of cloud and rainfall near the equator that typically recurs every 30 to 60 days.
“Now rainfall will reduce significantly over the Western parts of the country but it will continue over eastern parts of the country for a few days,” he added.
HT reported on Friday that there is about a 95% chance that 2023 will be the warmest or the second-warmest year on record according to a briefing by National Oceanic and Atmospheric Administration (NOAA). NOAA warned that several more months — possibly stretching into 2024 — could continue the heat trend thanks to the El Nino weather pattern remaining strong.
Mohapatra said a forecast will soon be issued for the post monsoon period of October-November-December but normally temperatures are expected to be above normal during a strong El Nino period. “Usually, winters are not expected to be very cold but apart from El Nino there are many other local factors that matter,” he said.
El Nino is characterized by an unusual warming of waters in the eastern equatorial Pacific, which has a high correlation with warmer summers and weaker monsoon rains in India. Positive IOD on the other hand is good for southwest monsoon over India. IOD refers to the temperature differential between the western and eastern Indian Oceans. A positive IOD has a direct correlation with a good monsoon.
The monsoon is critical for India’s economy as 51% of India’s farmed area accounting for 40% of production is rain-fed. As many as 47% of the country’s population is dependent on agriculture for livelihood.