A low-pressure area is likely to form over the South-East Bay of Bengal and the adjoining Andaman Sea during next two days, which could likely render conditions favourable for the advance of the 2020 South-West monsoon into parts of South-East Bay, the South Andaman Sea and the Nicobar Islands around May 16.

This is around normal time for the monsoon onset over the Andaman & Nicobar Islands, the farthest outpost in the territorial waters to receive the rains. The normal sequence suggests that by mid-May, the monsoon enters the Maldives (the Arabian Sea arm), followed by Myanmar (the Bayarm) and Sri Lanka, before hitting mainland India along the Kerala coast around June 1. The India Meteorological Department (IMD) will, over the next few days, announce the date of onset over Kerala.

Thunderstorms in Maldives

The Maldives Meteorological Service said that scattered rain, with occasional thunderstorms, may lash the atolls today (Tuesday). Showers may be heavy at times over the southern atolls and parts of the North. Winds will be from west-to-north-westerly at 21-37 km/h in the southern-most atolls and 10-16 km/hr elsewhere and may gust to 72 km/hr at times. They have to turn westerly-to-southwesterly to bring in the monsoon. The seas are expected to be moderate (wave heights of 4-8 ft) becoming rough (8-13 ft) during showers in the southern-most atolls and moderate elsewhere until Wednesday.

The Myanmar Department of Meteorology and Hydrology has said in its 10-day outlook issued on May 8 that the monsoon is likely to set over the southern parts of the country any time during May 16-21, which is around normal. During this period, the monsoon will be moderate, it said. The outlook went on to suggest that a low-pressure area may form over the South Bay and go on to further into a depression, which more or less rhymes with the IMD’s own outlook.

Comes full circle in Bay

Thus the weather over the larger Bay has come full circle, having initially defied the IMD that had declared a watch for the first pre-monsoon low by April 29. This was withdrawn after the system failed to meet a successive deadline later and weakened, leaving only a rudimentary cyclonic circulation in place. Global models did hardly any better, with predictions going awry, thanks mainly to atmospheric and oceanic patterns pulling in different directions.

The IMD, to its credit, had kept the remnant circulation under watch for signs of further development, which are likely on display concurrently. In fact, the IMD expects the emerging low to become marked two days after formation (around May 18). According to the Myanmar agency, it was partly cloudy to cloudy over the Andaman Sea and South Bay on Tuesday on Tuesday and partly cloudy elsewhere over the Bay.

Pre-monsoon showers

Meanwhile, the pre-monsoon thunderstorm continues unabated over the South, East and North-East of the country even as an approaching western disturbance would create volatile weather over North-West India. The IMD has predicted scattered to fairly widespread rain/thundershowers over the hills (Jammu & Kashmir, Himachal Pradesh and Uttarakhand) and the plains during May 13-15. Isolated thunderstorms accompanied with hail, gusty winds and lightning are also likely during the same period.

A typical pre-monsoon trough/wind discontinuity (where opposing winds meet) would cause isolated to scattered rain/thundershowers over Central India and the South Peninsula for next four days. Thunderstorms accompanied with lightning and gusty winds (30-40 km/hr) are also likely over the region. Heavy rainfall is indicated for Kerala, Coastal and South Interior Karnataka and Lakshadweep during May 15-16. Squally weather is likely over Lakshadweep and Andaman & Nicobar Islands during May 14-16.

East and North-East

The North-Eastern States too may witness scattered to fairly widespread rain/thundershowers during the next five days. Isolated to scattered rain/thundershowers are likely over adjoining Eastern States during this period. There could be isolated thundersqualls and heavy rain over Assam and Meghalaya on May 13 and gusty winds, lightning and occasional heavy rainfall over the rest of the region during these five days, the IMD said.

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