New Delhi

The India Meteorological Department (IMD) on Thursday announced the onset of the southwest monsoon over Kerala, officially marking the start of the country's four-month monsoon season.

The weather agency stated that the monsoon has advanced across the remaining parts of the southwest and southeast Arabian Sea, sections of the west-central and east-central Arabian Sea, the entire Lakshadweep region, Kerala and Mahe, as well as parts of Karnataka and Tamil Nadu. It has also progressed into the remaining areas of the Comorin region and further portions of the Bay of Bengal.

Kerala traditionally serves as the gateway for the southwest monsoon, which usually arrives around June 1 and subsequently spreads across the rest of the country during the June-to-September period.

The IMD had initially forecast the monsoon's arrival over Kerala on May 26, but the onset was delayed due to prevailing weather conditions.

Last week, the weather department revised its outlook for the season, predicting below-normal rainfall across the country. According to the latest forecast, India is expected to receive rainfall equivalent to around 90 per cent of the Long Period Average (LPA) during the monsoon season.

The LPA represents the average rainfall recorded over a long-term period, generally spanning 30 to 50 years. For the southwest monsoon season, the all-India LPA based on data from 1971 to 2020 stands at 87 centimetres.

Meteorologists classify seasonal rainfall below 90 per cent of the LPA as deficient.

One of the factors contributing to the subdued rainfall outlook is the possible development of El Niño conditions in the Pacific Ocean. El Niño is typically associated with weaker monsoon activity over the Indian subcontinent.

According to the IMD, the current neutral El Niño-Southern Oscillation (ENSO) conditions are gradually shifting towards El Niño. The weather agency expects these conditions to remain weak during June before strengthening to moderate or even strong levels by September.

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The monsoon remains crucial for India's agriculture sector, water reservoirs and overall economic activity, as a significant portion of the country's annual rainfall occurs during this period.