The Hindu Business Line : Monsoon eases as cold grips AP

THE alacrity with which the monsoon easterlies flagged themselves off to wallop the southern peninsula is wearing away, reducing the east-west shear zone of seasonal turbulence to tatters save a patch here and there.

Northeast monsoon will continue to be in a subdued state for the next four-five days, said Dr Akhilesh Gupta of the National Centre for Medium Range Weather Forecasting (NCMRWF). It is a passing phase, considering that November is the most `happening' month for the seasonal weather phenomenon.

The turn of events has to do with the fact that Wednesday's low-pressure area over southwest Bay of Bengal off the south Tamil Nadu-Sri Lanka coast has weakened a couple of notches by Friday. Reduced to an upper air cyclonic circulation by Thursday, it had become even less marked on Friday and was seen as a `northeast-southwest shear zone' over central Bay of Bengal, which Dr Gupta preferred to call it a seasonal trough.

Weakening of the Bay of Bengal prop had severely crippled the dynamics of the shear zone. On the western flank, though, the cyclonic circulation over southeast Arabian Sea that held the zone to point during peak activity persisted on Friday.

Model predictions have been indicating progressive weakening of the shear zone from Saturday onwards, and with it the northeast monsoon circulation pattern. This will lead to the shifting away of the maximum rainfall zone and further reduction in overall rainfall activity, which has already come to be noticed.

The easterly flows are still perceivable but will not by themselves be able to cause the heavy precipitation that marked the past week or two.

What these seasonal winds do best is to sustain the rain activity in some form over the peninsula until the next sea-based system takes shape. The NCMRWF has forecast light to moderate rainfall activity over the region during the next three-four days.

An interesting sidelight to the weakening of the monsoon system has been the incursion of untimely cold northwesterlies into north peninsular India that brought temperatures in some parts of Andhra Pradesh to record lows.

According to Dr Gupta, it is possible that the cold current may have ridden piggyback on the northwesterly component of the prevailing anti-cyclone over the mainland.

This happens whenever a deep western disturbance passes into the country from across the western border, and travels to the east. According to Dr Gupta, these disturbances have been queuing up on the border for sometime now.

The centre of the anti-cyclone has been located to a height of about three km at the latitude over Gujarat for the past two days.

But it is seen moving across to east from Saturday onwards in tandem with the western disturbance. The weak northeast monsoon regime should only abet this process, helping lift the cold weather over Andhra Pradesh.

On Friday, a western disturbance as an upper air system over north Pakistan and neighbourhood persisted. Under its influence, light to moderate rainfall/snowfall is likely at many places in Jammu and Kashmir and Himachal Pradesh.

The system is likely to move away by Sunday. Another system is expected to approach northwest India by Wednesday and cause isolated to scattered rains/snow in Jammu and Kashmir.

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