India’s west coast reports exceptionally heavy rain
Monsoon entered an active to vigorous phase over the west coast following the formation of a low-pressure area over the Bay of Bengal on Tuesday. The rain recorded in the past three days is unheard of, scientists said, even though they are yet to assess the historical data.Updated: Aug 07, 2020 11:43 IST
Several weather stations in the west coast, including the Konkan region; parts of coastal and south interior Karnataka; the Nilgiris in Tamil Nadu (TN), have received extremely heavy rainfall, measuring over 20 centimetres (20 cm), in less than 24 hours, triggering landslides, urban flooding and the largescale destruction of crops and properties since Monday (August 3).
Monsoon entered an active to vigorous phase over the west coast following the formation of a low-pressure area over the Bay of Bengal on Tuesday. The rain recorded in the past three days is unheard of, scientists said, even though they are yet to assess the historical data.
On Monday, Mumbai’s Dharavi got 38 cm rain; Santacruz and Colaba recorded 26 and 25 cm, respectively; and Hosanagar and Bhagamandala in Karnataka recorded 21 and 19 cm, respectively.
On Tuesday, Palghar recorded 46 cm; Talasari (39 cm); Dahanu (38 cm); Mahabaleshwar (32 cm); Khanvel (39 cm), while Vapi and Silvassa in Gujarat and Dadra and Nagar Haveli, respectively; Madikeri and Hosanagar in Karnataka; Jujumura and Nimpara in Odisha also recorded rainfall in excess of 20 cm.
On Thursday, Vaibhavwadi in Sindhudurg recorded 71 cm rain; Avalanchi in the Nilgiris recorded 58 cm; Bhagamandala (49 cm), Colaba 33 cm, according to India Meteorological Department (IMD) data.
“These are examples of an exceptionally high volume of rain recorded in a very short span of time: between Monday and Wednesday (August 3 and 5). Monsoon trough was weak and north of the normal position during the first three days of August. With the formation of a low-pressure area, the trough shifted southwards and became active during the second half of the week. Stronger southwesterly winds prevailed over the Arabian Sea between Monday and Wednesday, with Mumbai reporting up to 107 kilometres per hour (kmph),” said RK Jenamani, senior scientist, IMD.
“While it is too early for an in-depth analysis of the ongoing floods, what we can say is that there is an increasing trend in heavy rainfall events on the west coast of India. In our analysis of rainfall data over the last 70 years, we find a three-fold rise in extreme rains along the west coast and central India. This is because the monsoon winds over the Arabian Sea are now exhibiting large fluctuations due to a warmer environment,” said Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology, Pune, in a statement.
“Occasional surges in the winds drive a huge amount of moisture supply from the Arabian Sea, across the entire west coast. These episodes result in an intense rainfall spread over three days. Besides, some of my colleagues at New York University have found a slight northward shift of the monsoon westerlies in recent decades. This could mean that the chances of heavy rainfall might be larger towards the north of Western Ghats — but that aspect is yet to be explored,” he added.
“Monsoon was in its vigorous phase in association with the development of a low- pressure area. Southwesterly winds from the Arabian Sea were very strong. I cannot comment on each station but overall studies have shown that incidence of extremely heavy rain is increasing due to the impact of global warming,” said Dr. Mrutyunjay Mohapatra, director-general (D-G), IMD.
The monsoon trough is active and is south of its normal position (Ganganagar to the Bay of Bengal), according to IMD’s latest bulletin issued on Thursday.
Its western end is very likely to shift northwards gradually towards the Himalayan foothills on Saturday.
Now, the low-pressure area lies over southwest Madhya Pradesh. It is very likely to become less marked by Friday.
A cyclonic circulation also lies at north Konkan. Strong southwesterly/westerly monsoonal flow over the Arabian Sea with winds speed reaching 50-60 kmph along and off the west coast will continue till Saturday.
Very heavy rain is expected over Gujarat, Konkan, Goa, and Madhya Maharashtra (Western Ghat areas) and isolated extremely heavy falls likely over Gujarat on Friday. Extremely heavy rain over coastal Karnataka, TN, Kerala, and Mahe is expected until Sunday.
Another low-pressure area is likely to develop over west-central and adjoining north Bay of Bengal around Sunday. Under its influence, rainfall activity is likely to increase over east and central India again.
There is a 1% rain deficiency over the country since June 1, with 22% deficiency over northwest India; 5% over central India; 16% excess over peninsular India and 9% excess over east and north-east India.