Many areas in the Northeast are likely to get below normal rainfall during the upcoming four monsoon months (Representational Image)
Guwahati, June 3: Uncertainty surrounding this year's seasonal rainfall - which is forecast to be impacted by emerging El Nino conditions - became evident early, with the southwest monsoon missing its normal onset date in mainland India and contradicting earlier predictions by the India Meteorological Department (IMD).
The IMD had earlier forecast that this year, the southwest monsoon was likely to set in over Kerala on May 26 with a model error of (plus-minus) four days. After the seasonal winds missed its normal onset date of June 1, the national forecasting agency on Tuesday said the monsoon is likely to hit Kerala around June 4.
"Conditions are favourable for further advance of southwest monsoon into some more parts of southwest and southeast Arabian Sea, Lakshadweep Islands, some parts of Kerala and Tamil Nadu, some more parts of southwest, westcentral, eastcentral and northeast Bay of Bengal, and remaining parts of southeast Bay of Bengal around June 4," the IMD said.
Research scientist Dr Akshay Deoras said the monsoon winds had remained weak over the past few days, delaying its advance to mainland India.
"Weather models are indicating the possibility of a weak monsoon onset in Kerala after June 3, followed by its northward progression in the subsequent few days. Northeast India is expected to witness the monsoon onset between June 5 and 10," he said.
Normally, the monsoons cover Northeast India by June 5.
Fuelled by unusually warm ocean waters in the tropical Pacific, El Nino conditions are developing and are set to influence global temperature and rainfall patterns, increasing the risk of extreme weather over the coming months, the World Meteorological Organization (WMO) said on Tuesday.
Due to its impact, South Asia is expected to receive below average monsoon rainfall, according to the South Asian Climate Outlook Forum.
El Niño is characterized by unusually warm ocean surface temperatures in the central and eastern Pacific, which happen when easterly trade winds become weaker.
A strong El Niño typically reduces southwest monsoon's seasonal rainfall across India and tends to make the monsoon season warmer than normal. Of the 18 drought years in India in 100 years, 13 have been associated with El Nino.
According to the IMD's updated monsoon forecast, except the Kashmir region and some parts of Arunachal Pradesh and east coast of India, most of the remaining parts of the country are likely to get below normal rainfall this season.
Many areas in the Northeast are likely to get below normal rainfall during the upcoming four monsoon months, though the mean precipitation in the region as a whole may be normal.
The national forecasting agency has reduced its 2026 southwest monsoon rainfall forecast to 90 per cent of the LPA (long period average), down from its initial 92 per cent projection.
The Northeast has already witnessed five consecutive years of below normal monsoon rainfall. Last year, East and Northeast India recorded its second lowest monsoon rainfall (1089.9 mm) in the last 125 years, after 2013 (1065.7 mm).
Pre-monsoon rainfall in Assam has been around 11 per cent excess. Against the normal of 494 mm, the State had received 547.3 mm rainfall since March 1.
Relief from heat: Under the influence of various weather systems, fairly widespread to widespread light to moderate rainfall with thunderstorm, lightning and gusty winds (speed reaching 40-50 kmph) is likely over Northeast India during next five-six days. Isolated heavy rainfall is likely over Arunachal Pradesh during June 3-8 and Assam and Meghalaya during June 5-8. Maximum temperatures in the State have been above normal by 3 to 5 degrees at various places during the last few days.