An upper air cyclonic circulation has formed over Equatorial Indian Ocean off Sumatra coast (Indonesia) and adjoining South Andaman Sea on Friday, which could likely deepen as a fresh low-pressure area over adjacent south-east Bay of Bengal by Saturday (tomorrow). The India Meteorological Department (IMD) sees it tracking west-northwest and intensifying into a depression during subsequent two days while barrelling towards Sri Lanka and the Tamil Nadu coast in southern Indian peninsula.

An upper air cyclonic circulation has formed over the Equatorial Indian Ocean off the Sumatra coast (Indonesia) and adjoining South Andaman Sea on Friday. It is expected to deepen into a fresh low-pressure area over the adjacent southeast Bay of Bengal by Saturday. The India Meteorological Department (IMD) predicts it will track west-northwest and intensify into a depression during the subsequent two days as it moves towards Sri Lanka and the Tamil Nadu coast in southern India.

Likely next storm

A cyclonic circulation hovering over the Comorin area completes architecture of the build-up towards what is widely perceived as the next storm over the Bay, almost a month after severe cyclone Dana ran away to the north and east towards Odisha and West Bengal. The north-east monsoon had since relapsed into a lull except occasional thunderstorms over South Peninsula. 

Climate Prediction Centre of US National Weather Services sees upstream South China Sea also bristling with storm potential from November 27 to December 10 with implications for the Bay. It attributes this to a slowing of a passing Madden-Julian Oscillation (MJO) wave, progenitor of clouds, moisture, rain and storms as it passes periodically from west to east at higher levels.

Twin storm outlook?

This slowing of the ‘enhanced convective envelope’ set up by the MJO wave is likely to promote enhanced tropical cyclone activity across the Southern Indian Ocean (south of the Equator) and Bay during next two weeks (November 27 to December 3 and December 4 to December 10). Cyclone activity is also possible in the week from December 4 to 10 over the Western Pacific/South China Sea due to the MJO forcing, despite the basin known to stay comparably less active in December. 

The numerical weather model of the IMD too indicates the likelihood of twin storms forming over the Bay, though intensity may vary. In the first instance, it predicted the formation of a depression by Monday (November 25) but has not ruled out its further intensification into a possible cyclone. It said on Thursday ‘continuous watch is being maintained for further intensification and movement of depression towards Tamil Nadu coast’, especially the southern parts of the state, as also the Sri Lanka coast. 

Sri Lanka warning

The Sri Lanka Department of Meteorology has concurred, saying a low-pressure area is likely to form over south-east Bay of Bengal by Saturday. Thereafter, it is likely to intensify into a depression over south-west Bay (closer to Sri Lanka and Tamil Nadu coasts) during subsequent two days. The system may intensify further and move near the eastern coast of Sri Lanka. The department advised general public to be attentive to the future forecasts and bulletins in this regard. 

Rain over TN, Kerala

Tamil Nadu and Kerala have been reporting intermittent moderate to heavy rain during the past few days as the build-up continues over the Bay. The IMD has forecast isolated very heavy rain over south Tamil Nadu on Tuesday and over Coastal Andhra Pradesh and Yanam on Tuesday and Wednesday. To begin with, isolated heavy rain may lash the Nicobar region from Friday to Sunday as the sea churns with intensity to set up the ‘low.’ Isolated have rain is also forecast for Kerala & Mahe on Tuesday and Wednesday; south Tamil Nadu on Monday and Wednesday; and for Rayalaseema on Tuesday and Wednesday. 

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