As the Bay of Bengal waits for a low-pressure to spin up any time to its south-eastern basin (South Andaman Sea), first of the pre-monsoon season, Myanmar, one of its littoral countries, expects the South-West monsoon to break along its coast around the normal timeline of May 16-21 (usual date of onset over South Myanmar is May 18).

The Myanmar onset dynamics are important inasmuch as it more or less coincides with that over the Andaman & Nicobar Islands, the farthest outpost in India’s territorial waters. This is followed by onsets in almost clock-work precision over Sri Lanka soon after (around May 22) and on the Kerala coast along mainland India on June 1. The India Meteorological Department (IMD) will come out with onset forecast for Kerala by mid-May.

Negative IOD

The IMD has already forecast a normal monsoon for India this year, after the bumper year of 2019. A strong positive Indian Ocean Dipole (IOD) that drove the surplus monsoon last year could well be replaced by its alter ego, the negative IOD, as per latest assessments by global models. The overall monsoon may not be impacted thanks to a friendly La Nina evolving in the East Equatorial Pacific later, with warmer and cloud-building waters migrating to the Central and West Pacific, closer to Asia.

The Myanmar Department of Meteorology and Hydrology has said that it expects at least two low-pressure areas to form in the Bay of Bengal from end-April into mid-May, one of which may go on to intensify into a depression. The Bay is currently witnessing the genesis of the second mentioned, with the IMD putting out a forecast for it to become a depression with chances of further intensification.

Maintains storm track

The IMD maintains a North-North-West track for the storm initially and North-North-East later eyeing the Myanmar coast. It has also issued alerts on squally weather, high winds, and heavy rain warning over over the South Andaman Sea, the Nicobar Islands and adjoining South-East Bay during the next few days. On Thursday afternoon, strong south-westerly winds had helped mass up heavy banks of clouds extending from South Sri Lanka and adjoining East Equatorial Indian Ocean and South-West Bay.

The Sri Lanka Met Department said that there is no clear signal with respect to rainfall trends for the island nation during April-May-June. This means that there is equal chances for having below, about or above normal rainfall over those parts of the island. But there is a possibility for below normal rainfalls in southern coastal areas as well as some parts of Eastern province, particularly in Ampara, and Batticaloa, the national forecaster said.

June outlook

Meanwhile, the 11 global forecast producing centres of the World Meteorological Organisation situated in various countries (Australia, Brazil, Canada, China, France, Japan, South Korea, the Russian Federation, South Africa, the UK and the US) seem to bet on moderate to strong rainfall for Kerala and neighbourhood during the monsoon onset month of June. Only Brazil, South Korea and the Russian Federation centres have predicted below normal rainfall.