Not only did this year’s monsoon set in on schedule on 1 June and retreat late, it advanced across the country at its fastest pace ever in at least 72 years.

“The pace of advance of southwest monsoon this year had been the fastest during the period 1941-2013,” according to an end of southwest monsoon season report released on 17 October by India Meteorological Department (IMD).

This year, all of India received rainfall by 16 June; typically the monsoon covers the entire country only by 15 July.

This season, the country also saw extreme weather conditions, including heavy rainfall that caused flash floods and landslides in Uttarakhand, leading to the death of 580 people, according to government records. Some 5,359 people (938 locals and 4,421 pilgrims) are still officially “missing”.

Weather scientists have described this year’s monsoon as remarkable. There has not been much let-up in the rains, which started in the subcontinent earlier than expected. The monsoon, which arrived on 1 June over Kerala this year, is finally withdrawing from the country in the latter half of October. India receives over 75% of its mean annual rainfall from June to September. July and August are the peak monsoon months, which contribute about 61% of the total seasonal rainfall.

Incessant rainfall associated with the monsoon, low pressure systems and active monsoon conditions often caused flood situations in various states during different parts of the season, the IMD report said. Uttarakhand received 1,440% more rain than it usually gets by 18 June. The report maintained that the interaction between the monsoon low and the trough in the westerlies during the advance phase of the monsoon caused severe floods during 16-17 June in Uttarakhand.

Similarly in Gujarat, the rainfall received by Rajkot in Saurashtra, even while the monsoon was in retreat, during the 24-hour period ended 26 September was a record 39.2cm for the region. Thousands of people were evacuated from Vadodara and Bharuch districts of Gujarat in the last week of September after floods in the Saurashtra and Kutch regions. “Rainfall of such intensity is abnormal, but not unusual for this time of the year, when monsoon is retreating,” said D. Sivananda Pai, chief monsoon forecaster.

Kerala, too, saw intense rainfall this year. “It saw intense rainfall in the months of July and August and the dams were exceptionally full,” said M.R. Ramesh Kumar, chief scientist, physical oceanography, National Institute of Oceanography.

A research paper authored by V. Krishnamurthy in 2011 suggests that an increase in extreme rainfall events is occurring at the expense of weaker rainfall events over the central Indian region, and in many other areas. With a declining number of monsoon depressions, the upward trend in extreme rainfall events may be due to enhanced moisture content or warmer sea surface temperatures in the tropical Indian Ocean, the paper stated.

This year’s monsoon shows that parts of central India had deficient rain. The IMD report said many districts of Jharkhand and Bihar experienced moderate to extreme drought conditions during most part of the season. Various districts of Arunachal Pradesh, Assam, Meghalaya, Nagaland, Manipur and Mizoram were also dry and experienced drought conditions.

Similarly, the department reported that the east and NorthEast region received 28% below normal rainfall this year although the country as a whole received 6% above normal rainfall during the southwest monsoon. “All four regions in India received normal or above normal rainfall, except the eastern and northeastern states,” it said.

Monsoon is crucial for agriculture as 60% of the net sown area is dependent upon rains for irrigation. The share of agriculture in the gross domestic product in 2012-13 was 13.7%.

“It is true that there seems to be some tendency for the monsoons to be long-drawn, but it would be too early to say that it is a trend,” said Abhijit Sen, a member of the Planning Commission. “So to say whether farmers should change cropping patterns because there is a change in the rainfall pattern would be premature. Having said that, agriculture has always been a gamble with nature. It is highly dependent on rainfall and rainfall can be predicted only up to a certain extent.”

Pronab Sen, chairman, National Statistical Commission, said last year’s monsoon was delayed so the cropping pattern changed in favour of short-duration crops like pulses. “In India, the effect of prolonged winters is related to the danger of floods, which could then damage crops,” he said. “But broadly for the winter crop this means that there will be soil moisture and water in reservoirs. This will have a positive effect on the rabi, or winter crop, which is largely not a rain-fed crop.”

Long tail

This year’s monsoon has also been marked by a late withdrawal. The withdrawal line of the southwest monsoon was passing through Kalpa (Himachal Pradesh), Hissar (Haryana), Jodhpur (Rajasthan) and Naliya (Gujarat) from 19 September to 17 October. “The withdrawal of monsoon is very much delayed this year. It should have withdrawn from these places by 15 September,” said chief monsoon forecaster Pai.

The IMD report said that the successive formation of two low pressure areas and their westward movement across the central parts of the country caused the east-west trough to remain active, contributing to above-normal rainfall during September. “This development has stalled the further withdrawal of southwest monsoon,” it added.

The calendar of the monsoon is in flux, said Jatin Singh, chief executive of private forecaster Skymet Weather Services Pvt. Ltd. “Monsoon 2013 is peculiar because the monsoon started early and it is continuing post September,” he added.

Globally, monsoon onset dates are likely to advance or not change much while monsoon withdrawal is likely to be delayed, resulting in a lengthening of the season, said the latest Intergovernmental Panel on Climate Change (IPCC) report released on 30 September. The IPCC report also adds that “there is evidence that for peaks in the 11-year solar cycle, the Indian monsoon is intensified”,

Ramesh Kumar said that rainfall distribution is not continuous within the cycle of a monsoon, but is associated with multiple spells of active and break phases. “Break days generally become detrimental for agriculture, but there were no prolonged breaks in this year’s monsoon,” he said.

A paper authored by Ramesh Kumar and R. Krishnan, which examined daily rainfall over India for the period 1951–2007 shows that there has been a significant increase in the incidence of prolonged monsoon breaks, during the core monsoon months of July and August, over the subcontinent in the recent decades. It adds that prolonged breaks in the rainfall during July and August can create drought in the country.

Ragini Verma contributed to this story.