Goa likely to receive moderate rain in first week
New Delhi: India is likely to receive above-normal rainfall in September, capping a season that has already seen several disasters triggered by heavy downpours in many parts of the country.
The India Meteorological Department (IMD) said on Sunday that the monthly average rainfall in September is expected to be more than 109% of the long-period average of 167.9 mm.
Light to moderate rainfall is very likely in Goa in the first week of September, while heavy rainfall is likely at a few places in the state, according to IMD. Goa crossed the symbolic 100-inch rainfall mark last week following heavy rains that lashed the state after a lull of five days. The surge, which coincided with Ganesh Chaturthi festivities, disrupted normal life at several places.
The national forecast by IMD suggests that most regions will get normal to above-normal rainfall, while some parts of the northeast and east, many areas of extreme south peninsular India and pockets of northwest India are likely to record below-normal rain.
Addressing an online press conference, IMD Director General Mrutyunjay Mohapatra warned that heavy rainfall in September may trigger landslides and flash floods in Uttarakhand and could disrupt normal life in south Haryana, Delhi and north Rajasthan.
“Many rivers originate in Uttarakhand. So, heavy rainfall means many rivers will be flooded and it will impact cities and towns downstream. So, we should keep this in mind,” he said. He said that heavy rainfall is also expected in the upper catchment areas of the Mahanadi river in Chhattisgarh.
Mohapatra said there is a slight increasing trend in September rainfall since 1980, barring less rainfall in the month in 1986, 1991, 2001, 2004, 2010, 2015 and 2019. He said the normal date for the start of monsoon withdrawal from Rajasthan has shifted from September 1 to September 17, which itself indicates that rainfall activity in September has increased.
“September is a transitional month when the season moves towards the post-monsoon phase. With the withdrawal delayed, the chances of interaction between the monsoon and western disturbances rise. The frequency of these disturbances also increases as winter approaches. As a result of these encounters, September rainfall is showing an increasing trend,” the IMD chief said.
India received 743.1 mm of rainfall between June 1 and August 31, about 6% above the long-period average of 700.7 mm, IMD data show.
June rainfall was 180 mm, around 9% above normal, with large surpluses in northwest and central India. July brought 294.1 mm, around 5% above normal, led by a 22% surplus in central India. August added 268.1 mm, 5.2% above normal.
Mohapatra said northwest India recorded 265 mm of rainfall in August, the highest for the month since 2001 and the 13th highest since 1901. The region has experienced above normal rainfall in all three months of the monsoon season so far. Cumulatively, northwest India has received 614.2 mm of rain between June 1 and August 31, about 27% higher than the normal of 484.9 mm.
South peninsular India recorded 250.6 mm of rainfall in August, about 31% above normal, making it the third highest for the month since 2001 and the eighth highest since 1901, according to the IMD.
Cumulatively, the region received 607.7 mm of rain between June 1 and August 31 against the normal of 556.2 mm, a surplus of 9.3%. Mohapatra said unusually high rainfall in northwest India was triggered by strong interactions between western disturbances and monsoonal low-pressure systems.
He said that low-pressure systems from the Bay of Bengal, instead of following their usual path through Odisha, moved across Gangetic West Bengal, Jharkhand and Uttar Pradesh or via north Andhra Pradesh, south Odisha, Chhattisgarh and Telangana.
“Northwest India saw three such active interactions in August, which led to incidents in Dharali (Uttarakhand), Kishtwar (Jammu and Kashmir), Jammu and Mandi (Himachal Pradesh),” he said.
The heavy downpour in northwest India resulted in one of the worst floods in Punjab in decades, with swollen rivers and breached canals inundating thousands of hectares of farmland and displacing lakhs of people.
In the Himalayan states of Himachal Pradesh, Uttarakhand and Jammu and Kashmir, repeated cloudbursts and flash floods triggered landslides and caused widespread damage to life and property.
He said the IMD has not found any increasing trend in incidents of cloudbursts. However, he said, a study by the Indian Institute of Tropical Meteorology shows an increasing trend in mini cloudbursts, defined as rainfall of 5 cm or more in an hour.
Mohapatra said active western disturbances between July 28 and August 14 triggered heavy to very heavy rain over the western Himalayas and adjoining plains, causing a flash flood and landslide in Uttarkashi on August 5 and major riverine floods in Uttar Pradesh and Bihar.
He said the monsoon revived rapidly from August 14, with four low-pressure systems sustaining active conditions for 15 days in the second half of the month.
The IMD chief said northwest India and adjoining western Himalayan states experienced “extremely and exceptionally heavy rainfall events” between August 21 and 27 due to successive active western disturbances and strong monsoonal winds.
