There is no sign of the retreat of the south-west monsoon the India Meteorological Department (IMD) said.
Normally, the monsoon starts withdrawing in the first week of September. However, this has been delayed by more than two weeks this year. . “Withdrawal of the monsoon is not expected immediately. We are not meeting the retreat criteria. Rainfall is continuing. Retreat was to begin on September 1. We do not have any indication for retreat to begin in the next five days,” said K Sathi Devi, head of the National Weather Forecasting Centre.
“We are seeing this trend of delayed monsoon retreat in the past one decade. This may be because of interaction with extra-tropical systems or systems developing in Bay of Bengal. There is now good rainfall even in the later part of monsoon in September,” said AK Srivastava, head, climate change research division of IMD Pune.
This year, the onset of the south-west monsoon was also delayed by a week; it hit Kerala on June 8, instead of its scheduled date of June 1. This was followed by extreme deficiency of rain in June, which ended with a deficit of 33%, and as on September 17, there is a surplus of 4%.
The IMD had forecast a near-normal monsoon in May at 96% of long period average. This year, there were at least 1,400 heavy and extreme rain events during the monsoon months, of which more than 1,000 were recorded in August.
The number of heavy and extremely heavy rainfall days was the highest in August and July this year, as compared to the past four years, according to IMD Pune. According to the IMD, “a very heavy rainfall event” occurs when there is more than 12 cm rain in a day, and when the rainfall amount is 20 cm a day, it is called an “extremely heavy rain event”.
“In our long-range forecast, we had said rainfall will be normal or above average in the second half of the monsoon. Active rains in September and above average rainfall in central India are some of the peculiarities of this monsoon,” added Sathi Devi.
Temperature records also show that mean temperature for July was the highest ever in India due to “high minimum” or night-time temperature. The temperature in June was the fourth highest on record, and in August, it was the sixth highest on record in August for the same reasons, with floods and heavy rain causing 264 deaths across the country. During the monsoon months–June, July and August there were over 500 deaths due extreme weather events according to IMD.
Monsoon model projections show that the south-west monsoon, on which at least 700 million people are dependent for livelihoods, will become more unpredictable and intense in coming years.
A team from Indian Institute of Tropical Meteorology (IITM), led by R Krishnan, has developed an indigenous model to study the implications of climate change on the South Asian monsoon till 2100. “Our model is ready. We are still running some experiments on it. A preliminary analysis shows that with the rise in the global mean temperature, by the middle of the century the intensity of rainfall during monsoon will increase further and seasonal mean rainfall will also increase. These changes will intensify towards the end of the century till 2100,” said R Krishnan.
DS Pai, head, climate research services at IMD Pune, said, “Our data shows that extreme rain events are increasing, so are dry or light rainfall days. With a rise in global mean temperature, the moisture-holding capacity of the atmosphere increases, so there is intense rain during some spells.”
IMD in its Tuesday bulletin said there is likely to be another spell of very heavy rainfall ghat areas of central Maharashtra and Konkan regions on September 18 and 19. “The monsoon trough lies to the north of its normal position and is weak. However, under the influence of a cyclonic circulation over west-central Bay of Bengal off Andhra Pradesh coast, a low pressure area is likely to form over the region during next 24 hours. Subsequently, an east-west trough across northern parts of peninsular India is likely to get activated during September 18-20,” IMD bulletin said.
