Date:19/04/2006 URL: http://www.thehindubusinessline.com/2006/04/19/stories/2006041903080800.htm

Back Bay shaping up to host first pre-monsoon `low'

Vinson Kurian

Thiruvananthapuram , April 18

Preliminary indications of an evolving low-pressure area over a warming Bay of Bengal have been detected in what is considered as creating an enabling environment for pre-monsoon features to further establish over the Indian landmass.

Speaking to Business Line, Dr Akhilesh Gupta of the National Centre for Medium Range Weather Forecasting (NCMRWF), sea surface temperatures in the Bay are peaking to be able to host the first `low' of the pre-monsoon season.

Normally, the month of April witnesses two such systems, which, at times, have gone on to become even cyclones. These cyclones generally move northward skirting the peninsular coast and go to hit the Orissa or West Bengal coasts, or even further east. One such cyclone during April 1991 ravaged the Bangladesh coast and killed 1.29 lakh people in one of the worst-ever disasters in the Bay of Bengal basin.

Too early to predict

But Dr Gupta said it is too early to predict on how the prospective `low' over Southeast Bay would shape up. It all depends on where the low actually forms and how it manages to source the moisture feed. NCMRWF will mount a close a watch as the system evolves; it will be a day or two before it reveals itself in full flight. On an average, the Bay sees at least six tropical cyclones take shape on either side of the monsoon mean. Two of them turn up in the pre-monsoon season while the rest evolve later during the course of the monsoon and after it.

Another major weather eventuality helping pre-monsoon features to establish is the crucial April-time heating of the plains of North and Central India as well as the peninsular north. The ongoing thunderstorm activity in the peninsula under the influence of an easterly wave is expected to blow over in 24 to 36 hours. It is expected that mercury will then start peaking for at least a week to the desired levels.

Northwest

Ditto for North and Northwest India, where a prevailing western disturbance is currently spending itself out, paving the way for the sun to beat down hard over land. Apart from a westerly system of less-than-conventional amplitude, there is no other major weather system intervening to impinge on the heating process during the week.

A number of major weather models were in agreement with this general outlook. Most of them saw the Indian landmass `being devoid of any major rain activity' for the short but decisive term beyond April 20. This is in line with the NCMRWF outlook for the heating process to peak over land, Dr Gupta said.