The Hindu Business Line : Bay storm threatens to hit Lanka

Thiruvananthapuram, Dec. 4 India Meteorological Department (IMD) has said that Wednesday’s low-pressure area over southeast Bay of Bengal concentrated into a depression (numbered 07B) 630 km south-southwest of Port Blair, the nearest Indian administered region, on Thursday.

The storm was at a distance 1,200 km southeast of Chennai and 900 km east-southeast of Trincomalee, Sri Lanka, which is too low a positional coordinate to be of ‘direct threat’ to India’s southeast coast at least for the time being.

The projected west-northwest track would take it on a ‘landfall course’ with Sri Lanka at best, say model forecasts.

The Joint Typhoon Warning Centre of the US Military said on Thursday evening that 07B has might cross into the northeast Sri Lanka coast by Saturday night.

LIKELY CYCLONE

The models also say that the system has enough time and space to spin up as a tropical cyclone (likely to be named Bijli by protocol, the first India-given name after severe cyclonic storm Akash of 2007), given sea surface temperatures of 28 to 29 deg C ideal for storm breeding.

Initial model forecasts had suggested the northern tip of Sri Lanka for a landfall, and the adjoining southwest Bay and the Palk Straits for a break-away system to move toward the Tamil Nadu coast where the sea surface is comparatively cooler.

The Navy Operational Global Atmospheric Prediction System (NOGAPS) of the US Navy has consistently aired the view that the brewing storm would likely cross the Sri Lanka coast. On Thursday, this forecast found near-unanimous concurrence across a spectrum of peer models.

Among these were the Hawaii-based Joint Typhoon Warning Centre of the US Military; the Centre for Ocean-Land-Atmospheric Studies, again of the US; London-based storm tracker Tropical Storm Risk Group; and the European Centre for Medium-Range Weather Forecasts.

PEAK WINDS

Consensus forecast seems to suggest that the brewing cyclone would rustle up peak wind strength of 111 km/hr gusting to 139 km/hr on Saturday prior to landfall. This would go to make it a Severe Cyclonic Storm (Category-I).

South Tamil Nadu and adjoining Kerala too are expected to be impacted by the outer-propagating rain bands.

The odd NOGAPS forecast also suggested that another round of intensification may come about after a remnant system hops across Sri Lanka to emerge into the Gulf of Mannar or adjoining Indian Ocean (surface temperatures ranging from 29 to 30 deg C).

But this outlook lacked model consensus on Thursday.

WARMING SEAS

An IMD on Thursday seemed to indicate that the Arabian Sea may be gearing up to host the incoming system.

It said that a cyclonic circulation was traced to over the Kanyakumari area and neighbourhood.

The trough in the lower levels easterlies ran out from this system to the east-central Arabian Sea.

A pre-existing trough provides an incoming weather system the platform to grow.

An IMD forecast said that widespread with isolated heavy falls are likely over the Nicobar Islands during next 24 hours.

Squally winds reaching up to 45-55 km/hr in speed and gusting to 65 km/hr are likely over Nicobar Islands and the adjoining seas.

The sea condition is rough to very rough along and off the Nicobar Islands.