The Hindu Business Line : Cold, dry plains in north look west for rains

Thiruvananthapuram, Jan. 12 A western disturbance with an induced secondary cyclonic circulation is forecast to impact the western Himalayan region for four days from Thursday.

The plains of adjoining northwest India are expected to be affected on Saturday and Sunday, an India Meteorological Department (IMD) update said on Monday.

Meanwhile, a pre-existing western disturbance has not yielded place from its overnight perch over Jammu and Kashmir. It is expected to move away into the east-northeast in a day or two.

Sunday’s cyclonic circulation over Punjab has shifted to Uttarakhand and neighbourhood. Another cyclonic circulation was hovering over north Maharashtra and adjoining south Gujarat. The presence of the western disturbance coupled with the array of circulations has helped perk up mercury at a number of places over north, northwest and east India during the 24 hours ending Monday morning except in parts of Haryana and of north Rajasthan where it was below normal.

RISE IN MERCURY

Night temperatures are likely to increase by 3-4 deg Celsius over northwest India as early as from Wednesday from the warm and rising air at the front of the incoming disturbance. The US-based Centre for Ocean-Land-Atmosphere Studies suggests that parts of north and northwest India (including north and northwest Rajasthan, Punjab, Haryana, Delhi, west Uttar Pradesh, Uttarkhand, Himachal Pradesh and Jammu and Kashmir) may receive scattered rain during the week ending January 19.

The entire region (the Rabi belt) looks to western disturbances for bringing in the required moisture, but these systems have generally lacked the depth to sweep the sea surface to the southwest for the purpose. A building La Nina (cooling of sea surface temperatures) over the Equatorial Pacific may have proved their undoing.

LIKELY EXCEPTION

The incoming westerly system could be an exception with international models venturing to suggest that it would have the necessary attributes to induce a secondary cyclonic circulation with an embedded moisture pipeline from the northwest Arabian Sea.

Global Forecast Model runs by the Climate Prediction Centre of the US National Weather Services suggest that the upper-level westerly wind regime over northwest India would gradually grow vertically down to the southern Indian peninsula by January 20.

In the lower levels, easterlies-to-northeasterlies would continue to dominate the southern peninsula during this period but no significant burst in easterly wave activity is predicted during the period. Ambient conditions could change for the better towards the month-end, say some forecasts.

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