The India Meteorological Department (IMD) declared the onset of monsoon in India on Thursday, but the widespread characteristic monsoon rainfall would have to wait at least until next week.
The IMD said that during the past 24 hours, Kerala has received widespread rainfall. Clouding also increased over the southeast Arabian sea, and the strength of Westerly winds in the lower levels has increased and is about 19 knots.
This satisfies the conditions for the onset of monsoon. In the last 20 years at least, the onset of monsoon has never happened later than June 8.
Onset is declared when out of 14 selected meteorological stations on the Kerala coast, at least 60 per cent, that is at least nine of them, get at least 2.5 mm rainfall over two consecutive days. The onset marks the formal start of the four-month monsoon season that brings about 75 per cent of India’s annual rainfall. There are a few other accompanying criteria, relating to wind speed and pressure, which also need to be satisfied simultaneously.
But this onset is likely to be similar to a ‘soft landing’ and monsoon is expected to remain weak for at least one more week, thanks to the development of cyclone Biparjoy in the Arabian Sea. In normal course, monsoon spreads through most of southern India, and at least half of Maharashtra by June 10. As of now, however, the northern limit of monsoon continues to remain as far in the south as central Sri Lanka.The Biparjoy cyclone, which is expected to develop into a very severe cyclonic storm by June 13, is currently stationed around 850 km southwest of Goa in the Arabian Sea, and moving northwards at a slow speed. This cyclone is expected to result in rains along the entire western coast of the country, from Kerala to Gujarat, over the next couple of days. But the cyclone is also most likely to prevent the strengthening of the monsoon system, and further delaying its penetration over the Indian mainland. The northwards progression of the monsoon is unlikely to happen in the normal fashion till the cyclone subsides next week.
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