The Hindu Business Line : TN on alert as `Fanoos' heads for coast

NEGATIVE wind shear and positive sea surface temperature are seen aiding the intensification of Tropical Cyclone Fanoos to `severe cyclone' status by the time it makes a landfall on the south Tamil Nadu coast on Saturday.

India Meteorological Department (IMD) has indicated that crossover might take place during the noon hours but all six models run by the National Centre for Medium Range Weather Forecasting (NCMRWF) have tended to advance the same to the early morning hours.

`Eye-wall' formation: Dr Akhilesh Gupta of the NCMRWF told Business Line that the system, traced to 250 km east of Nagapattinam on Friday evening, had started showing signs of intensification. This was evident from a typical convective cloud build-up within the system, almost resembling an eye-wall, on Friday evening.

The markedly warming anomaly witnessed just to the south of Nagapattinam (as much as 1.5 deg Celsius) was where the storm was driving itself hard. In contrast, the waters north of Pondicherry were relatively cool, ensuring that Chennai escaped the brunt of the storm.

Still, Chennai and adjoining south coastal Andhra Pradesh will have to contend with some intense rain bands propagated by Fanoos as it slammed ashore.

Consensus predictions by various models indicate that the Vedaranyam-Pondicherry belt could be worst hit as the third cyclonic storm of the season rolled inland. Other landfall points being proffered were Mayiladuthurai (by the UK Met Office) and Pattukkottai (the Joint Typhoon Warning Centre, JTWC).

Storm surges predicted: Dr Akhilesh Gupta said that there are sensitive areas on the east peninsular coast that are prone to storm surges caused by the strong winds.

He singled out areas just south of Nagapattinam as the most vulnerable to these surges resulting in swells rising up to two metres.

A storm surge is water that is pushed toward the shore by the force of the winds swirling around the storm. This advancing surge combines with the normal tides to create the storm tide, which can increase the mean water level 15 ft or more.

In addition, wind driven waves are superimposed on the storm tide. This rise in water level can cause severe flooding in coastal areas, particularly when the storm tide coincides with the normal high tides.

Heavy rains: The JWTC observed that the system has managed to largely maintain its organisation overnight into Friday. The storm is expected to weaken as it approaches a region of higher vertical wind shear and drier air, and as the low level circulation interacts with land.

Under the influence of the landfall, coastal Tamil Nadu and south coastal Andhra Pradesh are likely to receive fairly widespread to widespread rains with isolated heavy to very heavy falls beginning from Friday. Strong winds clocking 60-70 km/h are likely to wallop the coastal districts of south Andhra Pradesh and Tamil Nadu beginning Saturday morning, the NCMRWF said.

Areas of scattered to fairly widespread rainfall activity will reach out progressively to Rayalaseema, south interior Karnataka, Kerala and entire coastal Andhra Pradesh.

Successor system: Projections by the European Centre for Medium-Range Weather Forecasting (ECMWF) said that the current spell of rain could extend to December 16.

The model even went on to forecast a successor system to `Fanoos' approaching the Sri Lanka-south Tamil Nadu coast by that time, in what is now turning out to be a remarkably wet northeast monsoon.

This system is also seen migrating from the South China Sea; the cloudiness being generated from there has seen no let-up for quite sometime now. Masses of cloud migrate in batches west into the Bay of Bengal waters setting up `lows' and storms in turn.

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