The Hindu Business Line : Tropical cyclone Rashmi crosses Bangladesh

Thiruvananthapuram, Oct. 28 The Bay of Bengal hosted the first tropical cyclone of the season on Monday as Cyclone Rashmi crossed the Bangladesh coast, farther northeast to a suggested location for landfall by model forecasts.

Strong westerlies took the storm veering away north-northeast as it bore down over Bangladesh before weakening progressively as a depression over Meghalaya.

On Tuesday, it has further weakened as a feeble ‘low’ over the same region, an India Meteorological Department (IMD) update said.

DRY PHASE

Simultaneously, a suppressed phase at the rear end of a passing Madden-Julian Oscillation (MJO) wave filtered into the equatorial Indian Ocean covering Sri Lanka and adjoining southern peninsular India to bring dry conditions.

The head-end that carries a payload of enhanced precipitation, which was active over the south peninsula till Monday, has since moved into the Bay of Bengal and adjoining South China Sea/Western Pacific.

This, along with the warmer than normal sea surface temperatures, would make both these seas the breeding ground for storms during the period leading up to November 10, according to the Climate Prediction Centre of the US National Weather Services.

The phase of active rains resulting from the passage of the next ‘wet’ MJO wave may be triggered from November 21 over Sri Lanka and the southern Indian peninsula. This phase would hold in varying intensity over the region until December 6, according to forecast by leading models.

SEA COOLS DOWN

Coastal Bay waters extending from Sri Lanka and further north along the Indian southeast coast to the Head Bay scorched by Cyclone Rashmi has cooled down appreciably ever since.

This corridor of cooler sea-surface temperatures (27-28 degree Celsius) would prevent any weather-making system from approaching the Indian coast at least until November 3, according to latest model assessment. The larger trough, a seasonal feature, is predicted to stay anchored over the Bay during this phase.

But the central and adjoining east Bay continues to be relatively warmer (28-29 degrees Celsius even touching 30 degrees Celsius in isolated cases), well beyond the threshold 27.5 degree Celsius for weather-maker systems to breed.

CYCLONIC WHIRL

And the IMD has traced an upper air cyclonic circulation over the central Bay on Tuesday. The swathe of cooler waters ahead and the westerly flows may take the system towards the Myanmar coast initially (until October 31).

The US National Centre for Environmental Prediction sees it then re-curving west-northwest to settle over north-central Bay adjacent to the ‘cool corridor’. It may head south to central Bay of Bengal and then west-southwest which places it on a course towards the Tamil Nadu coast (around November 3).