Monsoon season ends with 7.9% excess rain across country: IMD

THe sw monsoon flavor ended on tues, with the rural area receiving higher up normal rainfall at 7.9% excess rain compared to the long period average (LPA), the India Meteorological Department (IMD) announced.According to IMD, northwest India recorded 747.9mm of rainfall this season –– the highest since 2001 and sixth highest since 1901, while east and northeast India recorded second lowest rain since 1901.Most parts of the country are expected to receive normal to above normal rainfall during the post monsoon season –– October to December, except many parts of northwest India and some parts of extreme south peninsular India and northeast India, where rainfall is likely to be below normal, the IMD forecast.Further, in October, normal to below normal maximum temperatures are likely over most parts of the country, except northeast and adjoining east India, Western Himalayan states and Saurashtra and Kutch where above normal maximum temperatures are expected. There is, however, a high probability of above normal maximum temperature over northeast India. Above normal minimum temperatures are likely over most parts of the country with high probability over east, northeast and east central India during October, IMD has projected.Seasonal rainfall during October to December (OND) over south peninsular India –– consisting of five meteorological subdivisions (Tamil Nadu, Puducherry, Karaikal, Coastal Andhra Pradesh, Yanam, Rayalaseema, Kerala, Mahe, and South Interior Karnataka) –– is most likely to be above normal (>112% of LPA). The LPA of rainfall over south peninsular India during the post-monsoon season, based on data from 1971 to 2020, is about 334.13mm.The withdrawal of southwest monsoon from parts of west, central, east and peninsular India is expected to be delayed. This is due to a well marked low pressure area over the Gulf of Kutch and its neighbourhood. Isolated heavy rainfall is likely over the coastal areas of Saurashtra and Kutch during September 30 to October 2. There is likely going to be an increase in rainfall activity over east India during October 2-4, IMD has predicted.“Withdrawal of the southwest monsoon is expected to be delayed for the next one week from the rest of the country. It has already withdrawn from most of northwest India. We can expect withdrawal to commence once again from October 9 onwards,” M Mohapatra, director general, IMD said.Rainfall over the country during October is likely to be above normal (>115% of LPA). In October 2025, most parts of the country are expected to receive normal to above-normal rainfall. However, some areas in northwest India and extreme south peninsular India and isolated pockets in northeast India may experience below-normal rainfall, IMD said.La Nina to set in this monthMohapatra said that the sea surface temperatures over the equatorial Pacific are very close to La Nina threshold. “This means La Nina is approaching but it may be short lived. Below normal maximum temperatures may be expected over several parts of the country during the post monsoon season,” he added.La Nina refers to the periodic large-scale cooling of the ocean surface temperatures in the central and eastern equatorial Pacific Ocean, coupled with changes in the tropical atmospheric circulation, including changes in winds, pressure and rainfall patterns. Typically, La Nina brings climate impacts that are the opposite of El Nino (which refers to the warming of oceans), especially in tropical regions.IMD’s extended range forecast for the next two weeks shows widespread rain over the west coast till October 2 and widespread rain over central and east India till October 9.Above normal seasonal monsoon rainfallThe seasonal monsoon rainfall was above normal (>104% of LPA) at 107.9% of LPA. The summer monsoon rainfall was 937.2mm, which is the fifth highest since 2001 and 38th highest since 1901.There was 27.3% excess rain over northwest India, 15.1% over central India, 9.9% over south peninsula, and 20.3% deficiency over east and northeast India. Rainfall over northwest India was 747.9mm, which is the highest since 2001 and sixth highest since 1901.But, rainfall over east and northeast India was 1,089.9mm which is the second lowest since 1901. “The southwest monsoon seasonal (June to September) rainfall over the monsoon core zone, which consists of most of the rain-fed agriculture regions in the country, received 122% of LPA,” IMD said.Out of the 36 meteorological subdivisions, 2 subdivisions, covering 10% of the country’s total area, experienced large excess rainfall. Twelve subdivisions, constituting 35% of the area, received excess rainfall, while 19 subdivisions, representing 46%, recorded normal rainfall. The remaining three subdivisions –– Arunachal Pradesh, Assam & Meghalaya, and Bihar, accounting for 9% of the total area –– experienced deficient rainfall during the season.Monsoon arrived early, advancing over the South Andaman Sea and Nicobar Islands on May 13, nearly nine days ahead of the normal schedule. It arrived in Kerala on May 24, ahead of the usual onset date of June 1, and covered the entire country by June 29.There were seven monsoon depressions during the season, out of which only one intensified in to deep depression category. There were 69 low pressure system days against its normal 55 days. “Several large-scale factors helped the monsoon this year. These include neutral ENSO (El Nino Southern Oscillation) and IOD (Indian Ocean Dipole) conditions, low snow cover over the northern hemisphere, several low pressure areas .... Some of these also interacted with western disturbances which were also higher in frequency this year. All of these led to very favourable conditions for a good monsoon,” Mohapatra said.During September, rainfall over the country was 193.6 mm –– seventh highest since 2001 and 37th highest since 1901.“ENSO neutral conditions prevailed over the Equatorial Pacific. However, the sea surface temperature anomaly value was very close to La Nina threshold an d the circulation features were similar to La Nina. Further four low pressure systems formed during September alone. These were factors that led to good rainfall in September,” Mohapatra said.Monsoon fury claims 1,528 lives There were at least 1,528 deaths during the monsoon season, of which 935 were due to heavy rain and flash floods; 570 due to lightning and thunderstorms and 22 in heat waves, IMD said.Of these, 141 deaths were in Himachal Pradesh; 139 in Jammu and Kashmir, 41 in Uttarakhand; 290 in Madhya Pradesh among others.Among extreme weather events in September, IMD listed extremely heavy rainfall and cloud burst over Chennai; extremely heavy to very heavy rainfall over Telangana during September 11–15; extremely heavy rainfall spell over Uttarakhand and Himachal Pradesh during September 13-18 and associated flash flood and landslides; and extremely heavy rainfall at isolated places of Gangetic West Bengal on September 23 and Odisha on September 24. Extremely heavy rainfall event of 251.4mm occurred over Kolkata (Alipore) in a 24 hour period with near cloudburst threshold rainfall of 98mm between 3am and 4 am.