New Delhi: A very active monsoon from August 11 to 14, which brought widespread rain to northwest and central India, has wiped out the rainfall deficit that prevailed at the end of July and taken overall precipitation so far in the four-month season to excess at 103% of the long-period average (LPA).
Another low-pressure area is likely to form over the Bay of Bengal on August 19, according to the India Meteorological Department (IMD), which says it may trigger more heavy and widespread rains in the two regions.
Heavy rain triggered floods in a number of regions including Bihar, Assam, Arunachal Pradesh and parts of Meghalaya in July; Mumbai, Konkan and Karnataka in the first week of August; and flash floods in parts of Rajasthan on August 15.
Spurts of exceptionally heavy rain have paralysed life like they did this month in Kerala’s Idukki, where a landslide killed at least 55 people. According to a flood situation report dated August 12 by the ministry of home affairs’ disaster management division, 868 people have lost their lives to floods in 11 states, compared with 908 deaths in the same period last year.
“Yes, this year we have seen exceptional rains and several cases of extreme weather events. For example, one town in Jaipur district recorded 25 cm rain only in six hours. A lot of rain was recorded last week alone which helped northwest India largely cover its deficiency. Parts of Odisha, Chhattisgarh, Rajasthan have recorded extremely heavy rains in the past 24 hours,” said RK Jenamani, senior scientist at the National Weather Forecasting Centre.
“August will see excess rains because another low-pressure area is likely to develop over Bay of Bengal around August 19 which will bring very heavy rains to northwest and central India in the coming days. A fresh low-pressure area is likely to also develop around August 23 but we are not yet certain about that one,” Jenamani added.
Three low-pressure areas have already developed over the Bay of Bengal in August. These were the main rain producing systems during monsoon. No low-pressure area had formed in July and the monsoon trough (line of low pressure) had frequently oscillated towards the Himalayan foothills, bringing extremely heavy rains to northeastern states.
“The northern Arabian Sea has been anomalously warm during the last several weeks….the sea surface temperatures have been consistently 2-3°C above normal over this region. It has created a mini warm pool over that region, providing additional heat source and moisture,” said Roxy Mathew Koll, climate scientist at the Indian Institute of Tropical Meteorology.
“Our research shows that such high temperatures in the north Arabian Sea can lead to episodes of strong monsoon winds ensuing heavy rain spells across several parts of India,” Koll said.
June had ended with surplus rains of 17.6% while July had closed with a deficit of 9.7%. But the low pressure areas developing in August have intensified rains in the core monsoon region—parts of central and east India. According to IMD’s Sunday bulletin, parts of Chhattisgarh, Odisha, Konkan and Goa recorded very heavy to extremely heavy rains on Saturday and Sunday morning.
For example, Bhopalpatnam and Bhairamgarh 22 cm, recorded 32 cm and 22 cm of rain respectively; and Sama 27 cm and Bijapur 23 cm. All are located in Chhattisgarh,
The monsoon trough is active and lies south of its normal position (Ganganagar to Bay of Bengal.) Its western end is likely to move northwards during the next two days. A cyclonic circulation lies over south Punjab. Convergence of strong moist south-westerly winds from the Arabian sea over the plains of northwest India is likely to further strengthen from August 18 onwards.
Because of these conditions, increased rainfall is likely over northwest India from August 18 with widespread and heavy rains over the region and Uttarakhand. Extremely heavy rain is likely over west Rajasthan and Uttarakhand on August 18 and over north Punjab on August 19.
Extremely heavy rain is also likely over Telangana, Konkan, Goa, Vidarbha and Chhattisgarh, and the ghat areas of madhya Maharashtra on Sunday and Monday. Due to the likely formation of a low-pressure area, heavy to very heavy rain is likely over Odisha and Gangetic West Bengal also on August 18 and 19, IMD’s Sunday bulletin said.