The Met Department expects the monsoon to set in over Kerala by Friday, with conditions continuing to remain favourable to host the event along the southwest coast.

Onward progress of rains, at least initially, has a bias to the east with some parts of Tamil Nadu, Bay of Bengal during and the north-eastern States forecast to be the likely track.

An offshore trough along the Karnataka-Kerala coasts, a major monsoon feature, however, continued to be a feeble formation even on Thursday.

The helpful east-west shear zone of monsoon turbulence higher in the atmosphere too persisted.

But a land-based trough stayed anchored to the previous day’s alignment from southwest Madhya Pradesh to north interior Karnataka offered resistance to the monsoon flows from the Arabian Sea.

It is expected that the land-based trough would weaken with the onset of the monsoon.

Meanwhile, the India Met Department joined others in the watch for a rain-driving circulation (low-pressure area/depression) in the Arabian Sea off the Kerala-Karnataka coasts by the weekend.

Along coast This will ratchet up monsoon flows and lead to heavy rains along the south-west coast and interior peninsula. Initially forecasts suggest that the system may drive along the coast for sometime before steering off course out into the sea towards Karachi/Persian Gulf. Its behaviour and track would need to be tracked closely for its implications for the monsoon. A track along the coast would do a world of good for its orderly progress.

But if it were to steer off course and head out into the sea, it would mean that the monsoon flows and moisture embedded in them would get directed away from India.

For instance, the US Navy model says it could become a cyclone over central Arabian Sea and guide itself towards the Persian Gulf.

It may progressively weaken in strength as it approaches for a landfall and striking a pause off the coast of Oman by June 14, this forecast said.

A couple of other US models also favoured the intensification of the system in the central Arabian Sea, a safe distance away from India’s west coast.

The European Centre for Medium-Range Weather Forecasts begged to differ by picking up a low-pressure area curling its way along the west-coast towards Konkan-Mumbai during this period. It did not indicate strengthening of the system and merely said the monsoon flows would get strengthened, thanks to its pulling power.

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