August rainfall this year has been the highest since 1926 with 32.7 cm — or about 27% more than what is normal for the month, according to data from the India Meteorological Department (IMD) on Monday. In August 1926, the rainfall recorded was 34.8 cm, exceeding the normal by 33%.
IMD officials said that though August rainfall was in excess, the figure for this year’s monsoon as a whole were likely to be within the department’s June forecast of a normal (96 to 104% of the long period average) rainfall.
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“There has been a decrease in rainfall across India since the beginning of September. However we expect a revival again around September 17,” Mrutunjay Mahapatra, Director-General, IMD, said at a press conference on Monday.
From June to September 6, India had registered 7% more rainfall than what is normal for this period.
Also read: August receives 25% more rainfall; highest in 44 years: IMD
In the normal course, the monsoon begins its retreat from September 15 and this can go on for nearly a month.
Low-pressure systems
The heavy rain in August was due to several long-lasting low-pressure systems, or rain-bearing winds, that formed in the Bay of Bengal and were vigorous enough to travel all the way from the south-eastern coast up to north-west India. “In a typical monsoon season, there are 12-13 LPA. There were fewer this year, however, there were six of them in August and they lasted for several days. Together that led to several rainy days in August,” he said.
The surplus rain was primarily in Rajasthan, Gujarat, Maharashtra, Karnataka, Kerala, Telangana, Chhattisgarh and Odisha.
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Climate change
Long periods of heavy rain followed by extended dry periods are a feature of climate change and is part of a general change in monsoon patterns over India, the IMD had previously stated.
In response to a question from The Hindu , Mr. Mahapatra admitted that the agency’s monthly forecasts for July and August were widely off the mark, but said this was due to “intra-seasonal” variations and the IMD’s shorter-term forecast models had anticipated spells of heavy rain and adequately warned authorities.
This year the IMD launched urban flood forecasting services for Mumbai and Chennai and it would extend it to Bengaluru and Kolkata. “We can provide these forecasts for other cities too but require detailed maps of the cities. The [four cities] that we provided services were extremely cooperative and forthcoming with such data,” said Madhavan Rajeevan, Secretary, Earth Sciences Ministry. North-West India has seen 10% less rainfall than what is normal; Central India has seen a 17% surplus; South India a 20% surplus and Northeast India received exactly what it normally gets. Cooler than normal conditions in the equatorial Central Pacific contributed to the increased rainfall.
