Monsoon enters adjacent seas of Kerala; onset by tomorrow

The South-West monsoon has reached the South Arabian Sea, which is ‘within shouting distance of Kerala,’ as a feeble off-shore trough developed along the Kerala-Karnataka coast.

The rains have also entered the Maldives and the Comorin region apart from parts of South-West Bay of Bengal on Tuesday, the India Met Department said in its update.

Enabling feature The off-shore trough, an important enabling feature, is a receptacle of the monsoon flows headed towards the coast where the moisture mopped up from the sea gets accumulated.

Monsoon winds pump up this moisture against the heights of the Western Ghats where it cools to pour down in heavy torrents in a spectacular onset phase.

For this to happen, the currently ‘feeble’ off-shore trough has to deepen, which is expected would happen over the next couple of days.

The Met said that the onset along the Kerala coast is likely to materialise by tomorrow (June 9), two days after the mean of June 7 indicated in the onset forecast issued earlier but falling well within the four-day window extended to either side.

Logical conclusion Cross-equatorial flows (winds turning in from around the East African coast) are picking up in strength as a result of which the westerlies over the South Arabian Sea too have accelerated.

One thing leads to another in the onset sequence of things, and development of the off-shore trough on Tuesday was only a logical conclusion.

Deepening of the trough in a day or two will precipitate the onset over the Kerala coast, as mentioned earlier. The Met projects the monsoon flows ratcheting up in strength during the first week after onset.

This will make for a copybook-style onset phase with heavy to very heavy rain along the Kerala and Karnataka coasts to start with and would be replicated over Goa, Konkan and Mumbai in phases.

Equal distribution Global models are of the view that the monsoon flows would rally around the cyclonic circulations situated over East-central Arabian Sea (off Karnataka) and West-central Bay of Bengal off North Andhra Pradesh and South Odisha coasts to drive rains respectively along the West and East coasts.

This is expected to ensure equal distribution of rainfall over most of the southern peninsula even as it would tend to be heavy to very heavy along the West Coast.

As for the East Coast, the expectation is that the existing cyclonic circulation in the Bay would set up a minor storm, which would move along the coast towards Gangetic West Bengal and adjoining Bangladesh.

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