The Sri Lankan Met Department has this afternoon announced that 'South-West monsoon conditions are establishing over the island and surrounding seas.'

The announcement comes on the eve of the normal date of onset (May 25). Showery and windy conditions are expected to develop around the south and south-west of the island.

Kerala, which represents the south-west coast of India, will be the next gateway for the monsoon when it begins a four-month journey across the subcontinent.

'SHEAR ZONE'

Global agencies had said yesterday that the rains had arrived close to Lanka. Meanwhile, India Met Department (IMD) today saw the 'shear zone' in the South drift down to over the island by evening.

The presence of the 'shear zone of monsoon turbulence' means that the region under its footprint is preparing to host the annual rainy season.

Since yesterday, the IMD had located the zone, that rises from height of three km to six km in the atmosphere, over the South Peninsula.

But this has now moved down to the Sri Lankan latitude signalling the onset of the monsoon conditions there. This will move back later to South Peninsula to bring the monsoon to the Kerala coast.

OPPOSING WINDS

The shear zone is filled by opposing winds from a height of three km to six km, and represents the level in the atmosphere where the monsoon is most active.

This zone sets up the platform for rain-bearing systems (low-pressure areas/depressions) to play around in. The shear zone would strengthen further in consonance with the approach of the monsoon.

By the evening, a thick mass of cloud hung over north and north-east Sri Lanka and adjoining Gulf of Mannar that links South-East Tamil Nadu in peninsular India.

Another big bank of cloud hovered over South-West Bay of Bengal, some distance away from the Tamil Nadu coast, apparently rallied around by the prevailing cyclonic circulation in the Bay.

The clouding in the Arabian Sea was sparse in the morning but has grown across the southern fringes.

RAIN IN COMORIN

The IMD expects the monsoon to reach the southern Comorin area in next two days.

Thunderstorms and heavy rain has been forecast over the Lakshadweep Islands, Kerala, Coastal and South Interior Karnataka over the next few days.

Thunderstorms have also been forecast for Coastal Andhra Pradesh, Telangana, Rayalaseema, Tamil Nadu, and Puducherry.

According to the IMD, prospects of heavy rain are especially bright for Andaman & Nicobar Islands, Lakshsadweep, Kerala, Coastal and South Interior Karnataka from Saturday (May 27).

Heavy rain has also been forecast for the North-Eastern States in what is a pattern normally heralding the onset phase of the monsoon on the country's the south-west coast as well as in the north-east.

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