Much of India will witness another break in the monsoon from the middle of this week, but the hill states of Himachal Pradesh and Uttarakhand, battered by rains in August (and before that in July), could be set for another wet spell.
That’s because the monsoon trough is expected to shift northward towards north of its normal position during next two to three days, as confirmed by the India Meteorological Department on Monday. The underlying cause, experts add, could be the El Nino phenomenon.
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With the shifting of the monsoon trough northward, a second phase of weak or “break monsoon” is expected to begin. The monsoon trough was to the north of its normal position from August 7 to August 18 (11 days).
The first dry spell has already made itself felt in the overall numbers: monsoon rainfall to date is already 7% deficient, after ending July with a surplus of 5%.
“With the shifting of the monsoon trough northward, we can expect subdued rainfall conditions in the plains particularly northwest India and peninsular India. We can also expect heavy rainfall activity over the Himalayan foothills including Uttarakhand, Himachal Pradesh, north Bihar, parts of northeast India. We cannot say immediately when the trough will shift to normal position because conditions are fluctuating,” said M Mohapatra, director general, IMD.
The hill states are on alert as they face another possible deluge.
In Uttarakhand, the State Disaster Response Force (SDRF) has kept its personnel on standby with advanced equipment. “After weather alerts, our total strength of 560 at 42 locations across the state remains on alert. We remain ready with the raft, deep diving equipment, sonar system, drones, thermal imaging cameras, and other advanced types of equipment to deal with any situation,” SDRF commandant Manikant Mishra said.
“We ensure that our response time is minimal so that loss of human lives and damage to constructions can be reduced. We deploy our teams in flood-prone and landslide-prone areas to provide rescue and relief services in minimum time,” he said.
The director of Himachal state disaster management authority DC Rana said that the government was prepared to deal with any situation. “All concerned departments and officials have been put on alert. Rescue teams are prepared to move swiftly to flood and landslide prone areas. Men and machinery have been put in place to restore the roads in case of blockades,” he said.
HT reported on August 15 that northward movement of the monsoon trough, and its interaction with a weak western disturbance were responsible for the heavy rains in Himachal Pradesh and Uttarakhand that resulted in the deaths of at least 105 people across the two states in landslides, building collapses, and damage to roads and other infrastructure.
The monsoon trough is an elongated low-pressure area which extends from a so-called “heat low” (a low pressure over the seas) over Pakistan to the head of the Bay of Bengal region (parts of Odisha, West Bengal, and Bangladesh). This is one of semi-permanent features of monsoon circulation according to IMD.
The dry spell for most parts of the country could start as early as Tuesday, another expert said, and last till the end of the month.
“Break monsoon like conditions are expected to set in from Tuesday onwards. No weather systems are expected to form over the next 10 days that can bring the monsoon trough to its normal position. When weather systems such as low-pressure area or cyclonic circulations do not form the monsoon trough shifts to the foothills. With the shifting of the monsoon trough northward once again, we can expect heavy rain, landslides and mudslides in Uttarakhand once again on August 23, 24 and 25,” said Mahesh Palawat, vice-president, climate and meteorology, Skymet Weather.
El Nino is making its presence felt, he added.
“Moreover, the impact of El Nino on the atmosphere is clearly perceived now. During El Nino conditions, the sea surface temperatures over the eastern Pacific are very high, leading to high convection and clouding over South America but not so over the western Pacific and other parts. This also leads to a failure of the Indian summer monsoon. El Nino’s impact was felt over India only in August,” said M Rajeevan, former secretary, ministry of earth sciences.
“Monsoon trough is positioned northward for long time due to various reasons. One is a sinking motion or suppressed atmospheric conditions over central India which pushes the monsoon trough northwards. Sometimes western disturbance pulls it up. But the basic reason for long breaks is atmospheric dynamics associated with El Niño. El Niño impacts Indian monsoon through these long breaks,” he added.
El Nino has a strong influence on the southwest monsoon in India. El Nino is characterised by an unusual warming of waters in the eastern equatorial Pacific, which has a high correlation with warmer summers and weaker monsoon rains in India.