Second storm building over Arabian Sea, away from India coast

Global model forecasts are now indicating what is promising to be a busy fortnight for the Arabian Sea and the Bay of Bengal, with the onset of monsoon over the Kerala coast thrown in between.

India Met Department (IMD) has already indicated the onset date here as May 29, with a standard deviation of four days to either side of the median.

Littoral countries

This is three days earlier than the normal onset of June 1, but it would not be out of context to expect a surprise on the upside if it were to happen anytime before May 29.

This is based on the predicted state the Arabian Sea and the Bay going forward, based both on model forecasts as well as what is being assessed in real-time by Met agencies in the region.

If one were to draw from a soccer analogy, the monsoon approaches from the East first, with the Bay of Bengal 'arm' progressing in typical 'tiki-taka' style into the littoral countries.

Its clock-work 'passes' impact Myanmar, the Andaman & Nicobar Islands (within Indian waters) and Sri Lanka, before culminating in the ultimate 'goal' of an elaborate onset over the Kerala coast.

So it would be instructive to look at what is currently happening over the littoral countries and Andaman & Nicobar Islands, the first port of call in the territorial Indian waters.

Satellite image taken on May 20, 2018 at 09.15 IST. Source: IMD

MYANMAR

The Myanmar Department of Meteorology and Hydrology has said that the South-West monsoon may enter the country a little delayed than earlier thought.

The onset of monsoon over this country lying on the North-East fringes of the Bay is represented by a rhythmic escalation of rains over the Delta and Central Myanmar, one after the other.

The monsoon is now expected to enter the Delta in the South between May 21-25, later than median date of onset of May 18, which is the same for Andaman & Nicobar Islands.

The onset over the Andaman & Nicobar Islands that lie to the South-West of Myanmar in the Bay is now expected to happen on May 23, as indicated by the IMD.

But, significantly, the Myanmar Met has said that the monsoon would be heralded likely by a low-pressure area forming over the Andaman Sea and South Bay of Bengal.

'LOW' IN BAY?

This could likely go on to become a depression. A US model forecast is in agreement here, but not quite with the the likely strength or direction it might take in the Bay.

It would have a significant bearing on how the monsoon would be anchored from the Bay after twin away-going cyclones in the Arabian Sea disrupt the flows, after precipitating the monsoon.

The jump-start that the Arabian Sea has managed to get this year by spinning up cyclone 'Sagar' already and likely building a successor later this week, may have slowed the Bay down till date.

The IMD expects the Arabian Sea to spin up a preparatory 'low' by Monday, which would strengthen into a powerful cyclone headed towards the Oman coast.

The depression in the Bay would be the perfect anti-dote that the monsoon needs to keep itself on an even keel after the early cyclones in the Arabian Sea.

SRI LANKA

The Sri Lankan Met Department says that the monsoon conditions are currently getting established over the island.

This would mean that the onset can be precipitated anytime from now, and could likely happen before the normal date of May 25.

Sri Lanka is the penultimate port of call before the monsoon hits Kerala along India's South-West coast, five to six days after. Sri Lankan Met expects rains to its South-West to enhance later today.

Showers or thundershowers will occur at times over the Western, Southern, Sabaragamuwa, Central and North-western provinces, it said.

It has warned of very heavy falls of about 15 cm at some places in Sabaragamuwa in the South-West, one of the nine provinces in the country.

There may be temporary, localised strong winds during thundershowers. The public has been advised to take adequate precaution to minimise damages caused by lightning activity.

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