The Hindu Business Line : Weakened flows pare rain surplus to 5%

Thiruvananthapuram, Aug. 16 Monsoon has temporarily gone into a weak phase yet again, this time under the draining influence of a Category-5 Super Typhoon, named Sepat, raging to the east of the Philippines.

This was reflected in the paring down of the all-India seasonal area weighted rainfall surplus to 5 per cent as on Wednesday (August 15) compared with 7 per cent of the previous week. Still, 30 met sub-divisions had excess or normal rainfall, with only six (four, last week) posting deficits.

WESTERLY TROUGH

The current weak phase is attributed to the shifting of the monsoon trough to the foothills, western end up first, under the invasive impact of westerly trough in northwest India. The trough’s effect is expected to wear out over the next two days, paving the way for monsoon easterlies to wade their way in.

Earlier, in mid-July a comparatively less powerful typhoon Man-Yi that blowing away in a monsoon-harming north-northeast direction had hastened the ‘break monsoon’ phase that lasted a fortnight.

SHORTER BREAK

This time though, not only is the Super Typhoon moving in a west-northwest direction with benign implications for the monsoon, but the ‘break’ will also be much shorter. Sepat is predicted to slam the Taiwanese coast over the next two days and weaken in the process, allowing ample ‘window’ for Indian monsoon to breath in and resuscitate itself.

Model predictions promptly suggest that a middle-level cyclonic circulation would emerge over North Bay of Bengal in the next two days, which is expected to drop anchor as a low-pressure area.

This ‘low’ is expected to move in a west-northwest direction, roll over into central and north peninsular India, before culminating in a ‘blow-up’ of rainfall over Konkan-South Gujarat. It will later slide into the northeast Arabian Sea and head for Sindh in Pakistan.

WEST-NORTHWEST TRACK

According to domestic model forecasts, the ‘low’ will move initially across Orissa and Chhattisgarh. Fairly widespread to widespread rain is likely over Orissa and Gangetic West Bengal after the first 24 hours and subsequently over Chhattisgarh and Madhya Pradesh. Meanwhile, in the east, a north-south trough from Bihar to Head Bay of Bengal (a secondary trough) featuring an embedded upper air cyclonic circulation is seen as sustaining the fairly widespread rainfall with isolated heavy to very heavy falls over sub-Himalayan West Bengal, Sikkim, east Uttar Pradesh, Bihar and the Northeastern States for at least three more days.

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