Gulf of Thailand storm in focus ahead of N-E monsoon

While the North-East monsoon is expected to set in anytime, weather watchers are also looking at the prospects of a brewing storm over the Gulf of Thailand upstream to the immediate east of the Bay of Bengal.

Given that the winds have already turned north-easterly in the Bay as well as in the Gulf of Thailand/South China Sea, it is only to be expected that the storm would be driven straight into the Andaman Sea/South-East Bay of Bengal.

Likely storm track While the storm can help perk up the flows into the Bay, the moot question is whether it can hold on to a track to the west (aimed at the East Coast of India) or get directed elsewhere.

The US Climate Prediction Centre cited two model projections that suggested only a ‘low potential’ for depression/cyclone formation over the Bay during the week from November 1 to 7.

But others are far more convinced, with wind-field projections by the India Met Department (IMD) suggesting a northerly-to-northwesterly track in the Bay for a depression/cyclone that takes a swipe at the Myanmar and Bangladesh costs.

According to these projections, a prospective low-pressure area would already have become a depression within the Gulf of Thailand before it crosses Thailand’s ‘long tail’ to the South.

Differing model views It could become a tropical cyclone once it leaves the Chumphon province in South Thailand and enters the Andaman Sea by November 1 (mid-week next week).

The IMD projections take it along a north-northwesterly track along the adjoining coast of Myanmar and further north-northwest to the Bangladesh coast, as per forecasts valid until November 4.

From here, the natural course for onward movement suggests a landfall area around the coastal mangrove forests of the Sunderbans, which stretch from Bengal into southern Bangladesh.

But the European Centre for Medium-Range Weather Forecasts has an altogether different view. It shows the depression as slightly weakening as it nears the South Andamans by November 5 up to when forecasts are available.

Change in winds Winds over peninsular India, the Bay of Bengal, and the Arabian Sea have decisively changed direction to being easterly to northeasterly, signalling the end of the South-West monsoon.

The stage is now set for the onset of the North-East monsoon, indicated in a calibrated scale-up of rainfall over the South Peninsula and along the coasts.

The IMD seems to think that till such time as the Gulf of Thailand/Andaman Sea erupts in activity, the monsoon would mostly ride on an ‘easterly wave,’ the southern equivalent to western disturbances in North-West India.

Easterly waves are fast-moving low-pressure waves across the Bay and are frequent during the North-East monsoon. Some of the ‘rain heads’ packing the wave have in the past become lows, depressions, or even cyclones.

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