Private forecaster Skymet has declared that the South-West monsoon has arrived over mainland India along the Kerala coast in what it described as a ‘mild onset’. This is line in with its earlier prediction that the onset will happen on May 30 (Sunday) with a margin of +/-2 days.

But national forecaster India Meteorological Department (IMD) chose to push back the onset by four days to June 3 after south-westerly winds strengthen likely from June 1 resulting in enhancement of rainfall over Kerala. Hence, the onset may happen around June 3 against the predicted May 31 with a model error of +/-4 days.

Skymet Weather said that the monsoon kept date with Kerala two days before the normal date of June 1 despite two pre-monsoon cyclones, Tautkae and Yaas, to either side of the peninsula having robbed much of its kinetic energy. Prior to its arrival, most parts of the state have been receiving strong pre-monsoon showers.

Onset preconditions

GP Sharma, President, Meteorology and Climate Change at Skymet Weather, recalled that a set of environmental conditions must be fulfilled before the monsoon can be called over Kerala.

By and largeall parameters have satisfied the required threshold levels, especially rainfall and depth and speed of westerly winds over the South-East Arabian Sea and adjoining Equatorial Indian Ocean. Rainfall amounts are verified from the available data on the official website.

In the absence of any major monsoon trigger, the onset may lack vigour. Skymet Weather said that conditions are favourable for further advancement of the monsoon to more parts of the South Peninsula and the East-Central Bay of Bengal. A timely progress is expected also over North-East India.

Formation of cyclonic circulations on either side of the coastline in the first week of June will push and strengthen the monsoon current. Heavy rains with strong gusty winds are likely over the North Andaman Sea and the chain of Bay Islands, including Port Blair, Car Nicobar, Nancowrie, Hutbay, and Mayabander.

Moderate rains are likely over many places with isolated heavy falls over Kerala, Coastal Karnataka, and Lakshadweep. The sea condition is expected to be rough during this time.

Sharma had told BusinessLine on Saturday that the cyclones, especially Yaas that took shape closer to the onset of monsoon over Andaman Sea, had strengthened the cross-equatorial flows. “It was a copybook-style onset over Bay, South and North Andaman Sea, Sri Lanka, Maldives, and the Comorin.”

Kerala was the final stop. As on Saturday, it was almost there, at almost an arm’s distance from the coast. “Possibly one could look out through the window, and he could see it approaching,” Sharma had said.

The difference this time is that one doesn’t expect the resounding or thumping start to the proceedings. This assumes some meteorological conditions in the form of either a vortex over the Lakshadweep area or the adjoining South-East Arabian Sea, or in the form of an offshore trough along the West Coast.

A circulation coming up over the Andaman Sea or South-East Bay of Bengal, or closer home towards Sri Lanka coast or the South-West Bay of Bengal, or a depression somewhere coinciding with the onset of the monsoon could be the triggers of a spectacular onset. Any one of these could really do the honours, said Sharma.

“But I don’t find any. There are none today. It leaves the monsoon on its own to fire away. The flows heralded by the twin cyclones have fortunately sustained. Other than that, there is nothing. So, the onset will lack the spark. It will be a soft launch this time round, before the monsoon gains traction within the next three-four days.”