The Hindu Business Line : Rogue Bay system seen delaying `break monsoon'

A FRESH cyclonic circulation over the southwest Bay of Bengal that is bringing rain to Tamil Nadu as well as along the west coast, is seen pushing back the break monsoon phase by a day or two.

Various models now suggest that this circulation will persist for a minimum of three days, holding back a classic `break monsoon' for as many days from Saturday, an update by the National Centre for Medium Range Weather Forecasting (NCMRWF) said.

Speaking to Business Line, Dr Akhilesh Gupta, Director, NCMRWF, said the southwest Bay is prone to triggering such rogue systems in tandem with the ceasing of the seasonal `shear' activity over central India.

The shear activity will be at its peak during the active phase of the monsoon and does not allow the formation of any system over the adjoining Bay (in the latitudes north to the Equator up to 20N).

West coast anomaly: While the Bay system is to be expected in the run-up to the weak monsoon phase, it's the unanticipated spell along the west coast that is seen delaying the inevitable. `Break monsoon' presupposes subdued activity along the west coast. It's now case of fight for dominance between the prevailing westerlies in the northern plains and what Dr Gupta described as the `monsoon surge on account of a low-frequency oscillation of the 30-40 day-mode prevailing over the peninsula.' But all models indicate that this activity over the peninsula is temporary and that the westerlies will ultimately prevail.

In its official weather update, the NCMRWF said monsoon circulation features continue to indicate building up of favourable conditions for `break monsoon' situation to set in during Sunday-Tuesday. This is expected to cause increased rainfall activity over the northeastern States, foothills of the Himalayas and parts of southeast peninsular India. Precipitation over central India, the plains of the north and remaining parts of the peninsula will reduce after Sunday.

More rain for northeast: The cyclonic circulation over Bangladesh and neighbourhood persisted. It is likely to cause fairly widespread to widespread rainfall with isolated heavy to very heavy rainfall over parts of West Bengal and the Northeastern States during the next three days.

A western disturbance is likely to approach north Pakistan and adjoining Jammu and Kashmir by Sunday.

In the north and the northwest, scattered to fairly widespread rainfall is likely over west Uttar Pradesh, Uttaranchal and Himachal Pradesh during the next 24 hours, but will taper off thereafter. Remaining parts of the region may receive isolated to scattered rains during next 2-3 days.

In east and northeast India, scattered to fairly widespread rainfall is expected over east Uttar Pradesh, Bihar, Jharkhand and fairly widespread to widespread rainfall with isolated heavy rains over West Bengal, Orissa and the Northeastern States during the next four days.

In central India, scattered to fairly widespread rainfall is expected over Chhattisgarh, Madhya Pradesh and Vidarbha during the next 2-3 days. In the south, fairly widespread rainfall is likely over coastal Karnataka and Kerala, and isolated to scattered over the rest of the areas in the region during the next two days.

Scattered to fairly widespread rains are also likely over southeast peninsular India, viz. Tamil Nadu, Rayalaseema and south coastal Andhra Pradesh during the next three days.

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