Thiruvananthapuram, Dec. 22
INDICATIONS are that the new `low' expected to take shape by Sunday over the southeast Bay of Bengal will be a feeble one and might well turn out to be inconsequential for the peninsular coast.
The fast pace with which it is moving and the striking failure to grow markedly during the past 24 hours would give the impression that it is going to behave as an `easterly wave', said Dr Akhilesh Gupta of the National Centre for Medium Range Weather Forecasting (NCMRWF).
Predecessor Tropical Depression 07B also had started off as an easterly wave, which usually travels in a straight line to the west and carries weather only in the front. But 07B was made to swerve north-northeast from a westward-bound course under the influence of an incoming westerly trough.
In the case of the new system brewing, chances are that the significantly cooler waters along coastal Tamil Nadu and northeast Sri Lanka in combination with the increasing wind shear will prevent the system from foraying deep into the southwest Bay.
But the wind shear was showing signs of tapering off in a circle over the Andaman and Nicobar Islands, says the University of Wisconsin-Madison. Here is where the system will be hosted first in the territorial waters. But opinion is divided on which course it will take thereon.
The European Centre For Medium-Range Forecasts (ECMWF) has indicated that the cool waters in the southwest Bay adjoining Tamil Nadu will force it to turn southwest and drift towards southern Sri Lanka. This is a view supported by the National Centres for Environmental Prediction (NCEP) as well, which adds that it might go on to impact parts of southern Sri Lanka.
If anything, its now becoming increasingly clear that an eventful northeast monsoon is entering its last stages, Dr Gupta said.
The Inter Tropical Convergence Zone (ITCZ), the belt of convection encircling the globe and the fountainhead of monsoonal rain, is on its southbound journey and is now located close to the Equator. This transitional phase will culminate with the ITCZ crossing the Equator to nestle into its seasonal perch in the southern hemisphere by mid-January. It will rest there until next June when it heaves itself back to the north to trigger the next monsoon.
As for 07B, the final warning from the Joint Typhoon Warning Centre (JTWC) said it would dissipate as a significant cyclone over seawaters by Friday morning. But the UK Met Office said it might undergo another round of slight intensification on Saturday morning, weaken soon after and lie as a system below tropical storm strength by Sunday morning.
In its update, the NCMRWF said the system had weakened to being a well-marked low-pressure area on Thursday and lay centred over southwest and adjoining west-central Bay of Bengal.
It is likely to move further to the northeast and weaken but will bring scattered rainfall over coastal Orissa, West Bengal, Sikkim and the Northeastern States during the next two days.
Isolated to scattered rains are also likely over coastal Andhra Pradesh, the Andamans, coastal Tamil Nadu and Pondicherry during the period.