Severe cyclone Helen prowled the waters on a day when it kept changing its bearing over the west-central Bay of Bengal.

It gave nothing away with regard to location and track on Thursday, shifting both at will, and spooked weathermen on the watch.

LANDFALL LOCATION

The storm has delayed landfall by at least 24 hours and changed location lately to Machilipatnam in Andhra Pradesh. The crossover is expected into Friday evening only. Meanwhile, the US Joint Typhoon Warning Centre said that Helen may remain over water for the next 24 hours and gradually start weakening.

This is attributed to decreasing ocean heat content and increasing vertical wind shear. The cyclone needs warm waters to sustain the process of convection (cloud-building).

Vertical wind shear refers to sudden change in wind speed and direction with height due to external factors.

The storm tower rises 10-12 km in height and enhanced wind shear ‘shears off’ the top the storm, affecting its build and compromising its strength.

SUCCESSOR STORM

The agency did not rule out the possibility of rapid weakening in which case the storm will track more southwest than west.

Close on the heels of Helen, the Andhra Pradesh coast is threatened with the prospect of another likely cyclone early next week.

India Met Department has already said that a causative ‘low’ will form over the boiling cauldron of south-east Bay of Bengal around the time when Helen hits the coast. It will rapidly deepen into a depression, the Met Department said in its update on Thursday evening.

US Fleet Numerical Meteorology and Oceanography Centre sees another destructive cyclone in the making and barrelling towards Andhra Pradesh coast by Tuesday.

LANDFALL AREA

The area of landfall is projected to be the same one as Helen will hurtle into on Friday, according the US agency.

Meanwhile, the Met Department said Helen will have brought heavy to very heavy rainfall with isolated extremely heavy falls over north coastal Andhra Pradesh on Thursday.

On Friday, heavy to very heavy rainfall with isolated extremely heavy falls is forecast over north coastal Andhra Pradesh.

Isolated heavy to very heavy rainfall would break out over south coastal Andhra Pradesh, Rayalaseema and Telangana.

Gale winds reaching 100-110 km/hr and gusting to 120 km/hr would prevail along and off remaining parts of Andhra Pradesh coast. Sea conditions would be very high.

vinson.kurian@thehindu.co.in

(This article was published on November 21, 2013)
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