The Hindu Business Line : Northwest `high' compounds break-monsoon

A NON-SEASONAL anti-cyclonic circulation traced to the 700 hPa-level (3.1 km above sea level) over the northwest India on Monday has confirmed fears of meteorologists monitoring the progress of the southwest monsoon.

The circulation has caused large-scale downward motion (subsidence) of air, which inhibits the development of rain-bearing clouds over the region. Monsoon currents can flow only into a trough of `low' where the prevailing rising air yields place.

The prevailing anti-cyclone (high-pressure zone) will hold for at least the next 4-5 days, says Dr Akhilesh Gupta of the National Centre for Medium Range Weather Forecasting (NCMRWF).

Formation of the anti-cyclone during mid-monsoon is rare though a similar instance has come to be reported during the break phase of the 2002 monsoon.

Otherwise the `high', which brings about clear skies and pleasant mornings, is normally associated with the withdrawal phase of monsoon.

Fresh monsoon pulse

Meanwhile, model predictions by the European Centre for Medium-Range Weather Forecasts (ECMWF) suggest that monsoon will revive in the form of a `pulse' expected to break over Kerala/Karnataka by September 6/7. The Arabian Sea-generated system would hardly bring immediate relief to central and northwest India.

The fresh pulse is expected to traverse a southward-up course and drive up the system into central India in five days' time (around September 11/12). It is hoped that the Bay of Bengal would have warmed up sufficiently by then to create a `low' and swing back the monsoon trough into position from its perch along the foothills.

But this is still in the realm of conjecture, Dr Gupta said, and as such the break of the next `pulse' along the southwest and its progress would need to be closely watched.

An NCMRWF update said the southwest monsoon continued to be in a break phase on Monday with the seasonal trough lying close to the foothills. During the last 24 hours, most parts of the country have remained relatively dry.

During the next 3-4 days, rainfall activity will be mostly confined to the Northeastern States, sub-Himalayan West Bengal, Sikkim, North Bihar and south peninsular India with subdued rainfall activity over the rest of the country.

Sunday's upper air cyclonic circulation over Kerala and neighbourhood moved westwards and was centred over Lakshadweep area. A fresh upper air cyclonic circulation lay over south interior Karnataka and neighbourhood. These systems are likely to cause moderate rainfall activity over south peninsular India during the next two days.

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