Monsoon likely to be ‘above normal’ at 106% of LPA: IMD
During June to September, ‘normal’ to ‘above normal’ rainfall is very likely over most parts of the country, except some areas of northwest and east India.
The monsoon rains over India from June to September is likely to be 106% of the long period average (LPA) with a model error of ±4%, indicating that above normal rainfall is likely, the India Meteorological Department (IMD) said in its updated long-range forecast on Tuesday.
In April, the IMD forecast that the annual southwest monsoon rainfall is likely to be ‘above normal’ at 105% of LPA, with a model error of ± 5%. The seasonal rainfall is most likely to be above normal over central India and south peninsular India (>106% of LPA), normal over northwest India (92-108% of LPA) and below normal over northeast India (<94% of LPA), the IMD said. The LPA for the monsoon season based on the 1971-2020 period stands at 87 cm.
The seasonal rainfall over the monsoon core zone (MCZ), consisting of most of the rainfed agriculture areas in the country, is also most likely to be above normal (>106% of LPA).
Overall, there is a 32% probability of ‘above normal’ rain (105-110% of LPA); 27% probability of ‘excess’ rain (> 110% of LPA); 31% probability of ‘normal’ rain (96 -104% of LPA); 8% probability of ‘below normal’ rain (> 90 - 95% of LPA) and only 2% probability of ‘deficient’ rain (< 90% of LPA).
During June to September, normal to above normal rainfall is very likely over most parts of the country except some areas of northwest and east India and many areas of northeast India where below normal rainfall is very likely, the IMD has said referring to its spatial distribution forecast.
“We can say that monsoon is expected to be good over most parts of the country,” IMD director general M Mohapatra said.
The Met department has warned in its spatial forecast that “above-normal rainfall carries benefits for agriculture and water resources but also introduces risks such as flooding, disruptions to transportation, public health concerns, and harm to ecosystems”.
“To address these risks, strategies can include reinforcing infrastructure, making use of IMD’s early warning systems, strengthening surveillance and conservation initiatives, and establishing response mechanisms within sectors that are particularly vulnerable,” the weather department said.
The IMD is also expecting above normal rain in June over most parts of the country. To be sure, monsoon rain in May will not be accounted for, as the IMD considers monsoon season only from June to September.
Monsoon made its onset over Kerala on May 24, eight days before the normal date of June 1.
In June, normal to below normal day temperatures are likely over most parts of the country, except many regions of the northwest India and northeast India, where above normal temperatures are very likely. However, above-normal minimum or night temperatures are likely across most parts of the country, except some parts of Central India and adjoining south Peninsula where, where normal to below-normal minimum temperatures are very likely, IMD said.
Normally, two to three heat wave days are expected over NW India in June, but this time the IMD has said ‘below normal’ or hardly any heat wave days are expected over the region. But “people need to be cautious about humid heat and high night-time temperatures”, officials said.
Currently, neutral El Nino-Southern Oscillation (ENSO) conditions and neutral Indian Ocean Dipole are prevailing over the equatorial Pacific region. The latest Monsoon Mission Climate Forecast System (MMCFS) as well as other climate model forecasts indicate that the neutral ENSO conditions are likely to continue during the monsoon season, but weak negative IOD may set in. During this time, the hostile influence of El Nino is not expected on monsoon.
La Nina refers to the large-scale cooling of the ocean surface temperatures in the central and eastern equatorial Pacific Ocean, coupled with changes in the tropical atmospheric circulation, such as winds, pressure, and rainfall. El Nino is the opposite; it represents the warm phase of the ENSO cycle.
In India, an El Nino is associated with a harsher summer and weaker monsoon. La Nina, meanwhile, is associated with a strong monsoon, above average rains and colder winters.
However, naturally occurring climate events such as La Nina and El Nino are taking place in the broader context of the human-induced climate crisis, which is dialling up global temperatures, exacerbating extreme weather and climate, and impacting seasonal rainfall and temperature patterns, the WMO has warned.
On further progress of monsoon
“Monsoon made a classical onset and progressed very quickly over large areas in association with a monsoon vortex. A depression formed over Arabian Sea which helped its onset but all large scale and regional scale criteria for monsoon onset were also met. Now a low-pressure area has developed over Bay of Bengal, which will also help monsoon progress but after 3-4 days monsoon progress may slow down,” Mohapatra said.
HT reported on Tuesday that the progress of the southwest monsoon, which not only arrived eight days early in Kerala, but also covered large parts of the country including Mumbai on the west coast and almost all of northeast and peninsular India within two days, is likely to slow down after June 2, various models have indicated. This will be mainly due to mid-latitude dry air intrusions.
“Of course, when the weather systems gradually move away, a slowing down is expected,” M Ravichandran, secretary at the ministry of earth sciences, said.
“Farmers are advised to follow agro-met advisories to suitably time harvest,” Mohapatra added.
HT had reported that May has been unusual for northwest India, particularly because of persistence of slow-moving western disturbances (WD) over the region. WDs are cyclones originating in the Mediterranean Sea which move east and bring winter rain to NW India. The impact of WDs is felt normally during December, January and February but this year they have been active till late May. Normally the persistence of WDs is unfavourable for the monsoon, according to experts.
“Yes, WDs are persisting till summer this year. Monsoon has not progressed to NW India yet and hence we cannot say whether it will interact with these WDs. One of the main reasons we are seeing sudden, intense thunderstorm activity over NW India is the unusual persistence of these WDs,” Mohapatra said.
