Excess rain into first half, and June hopes to add more

Twelve days after the monsoon entered the Kerala coast, all-India rainfall continues to be in excess (32 per cent above normal) despite a few more meteorological subdivisions losing the early advantage gained from a surplus pre-monsoon rain and waited for the real monsoon rains to arrive.

In comparison, last year, the monsoon was delayed, sluggish and weak during this period after being confined to Western Ghats and covered only 10 percent of the landscape (normally close to 50 per cent). It had also totted up massive deficit of 42 per cent as away-going cyclone Vayu stole its thunder.

Over Mumbai in two days

On Friday, the India Meteorological Department (IMD) expected the monsoon to cover remaining parts of Maharashtra (including Mumbai), Odisha and West Bengal; some more parts of Chhattisgarh and some parts of South Gujarat, South Madhya Pradesh, Jharkhand and Bihar during next two days.

But it had fallen fresh into deficit over Lakshadweep (-29 per cent); Jharkhand (-32 per cent); and Nagaland-Manipur-Mizoram-Tripura (-28 per cent); West Uttar Pradesh (-32 per cent); and Jammu & Kashmir and Ladakh (-42 per cent), while improving over Tamil Nadu and Puducherry (-36 per cent).

Flows to strengthen

Seasonal rains may be lagging by a few days on the West Coast as well as in the North-East, but it is ahead of time over some parts of East India, especially the southern parts of Odisha and the contiguous Chhattisgarh, thanks mainly to a low-pressure area that washed over land from the Bay of Bengal.

Though it has not become well-marked, the low is expected to strengthen south-westerly monsoon flows from the Arabian Sea along the West Peninsular Coast prompting a large shield of isolated heavy to very heavy rainfall over coastal Karnataka to unfold over the next two days, the IMD said.

Blast along West Coast

It may unleash scattered heavy to very heavy with isolated extremely heavy rainfall over Konkan & Goa; isolated heavy to very heavy over Madhya Maharashtra, Marathawada, Coastal Andhra Pradesh, North Interior Karnataka, Chhattisgarh, Telangana, Vidarbha, Assam and Meghalaya into Saturday.

Scattered heavy to very heavy with isolated extremely heavy rainfall is likely over Vidarbha, while it would be isolated heavy to very heavy over Coastal Karnataka, Madhya Maharashtra, Chhattisgarh, Telangana, Assam and Meghalaya on Sunday during this vigorous phase of the monsoon.

Wind shear, the villain

The low lay over North Coastal Andhra Pradesh and adjoining Coastal Odisha on Friday noon but, contrary to expectations, failed to intensify a round despite enjoying warm waters earlier in the Bay. The vertical wind shear (change in wind speed and direction with height) could have proved fatal here.

With the monsoon having covered the entire Bay, the vertical wind shear would be high enough to tear apart any storm structure building in the region. This could have affected the prospects of the low, suspects Akhilesh Gupta, Advisor and Climate Change expert with the Department of Science and Technology.

After onset, the monsoon works on its own dynamics and in tandem with an existing low in the Bay. They co-exist and feed into each other in such harmony that one would not be able to live without the other. This is spectacularly on view in how the monsoon flows and the low in the Bay have behaved.

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