The monsoon has delivered a surplus of four per cent for the country as a whole during the June 1 to 22 period even as it looks to end June with a flourish over North India during the last week of the month.

Out of the areas already covered (mainly South Peninsula and North-East India), the monsoon has left behind a worrisome deficit of 32 per cent in Kerala and 23 per cent in South Interior Karnataka.

Rain distribution

The rest of the Met subdivisions have received either ‘normal’, ‘excess’ or ‘large excess’ rainfall during this period. Meanwhile, the monsoon is behind schedule by more than a week in Gujarat and Madhya Pradesh.

Most of North-West India has already received good precipitation due to good pre-monsoon activity, and this could be one reason why the monsoon proper has delayed its entry into Madhya Pradesh. Rains seek out those areas falling within a ‘trough’ created by the rising motion of air engineered by a merciless summer sun, leaving behind in its wake an elongated area of lower pressure (put simply, the trough) over land.

Since Madhya Pradesh has been receiving good pre-monsoonal rainfall, the peak heat was snuffed out early, which meant that there was no ready ‘trough’ in place to receive the monsoon as it raced in from the peninsula.

Fresh opportunity

The trough would have acted as the receptacle for the flows from the low-pressure areas that formed in the Bay of Bengal last week. In its absence, they strayed into Bangladesh, emptying themselves there and in the adjoining North-Eastern States of India.

But another window of opportunity is opening up in the Bay as a preparatory circulation has showed up over the North Bay of Bengal. The land-based trough is expected to link up with this to set up a likely rain-making low-pressure area.

The track the ‘low’ takes to move across land will determine the areas likely to be covered by the monsoon. Available indications suggest that the ‘low’ will cross into Central India and North-West India between June 25 and July 1.

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