Weather: Rain surplus rises to 4 per cent; deficits moderate

The overall rain surplus for the country as a whole until Sunday (June 1 –August 16) has risen to four per cent as an active monsoon trough with an embedded circulation from an erstwhile low-pressure area at one end pumped in strong and moist winds from the Arabian Sea even as a prevailing low-pressure area held up the other end.

The India Meteorological Department (IMD) located this low, weakened from being well-marked the previous day, over Jharkhand and neighbourhood on Sunday afternoon. This low is helping in a stream of easterly monsoon winds from the Bay of Bengal to converge overland with the south-westerlies from the Arabian Sea. 

Deficit over North-West moderates

It would continue to move towards North-West India and weaken further over the next two days. It is into these friendly monsoon settings that a new low likely forming in the Bay by Wednesday would throw itself in, and keep the monsoon trough alive over the plains of North India and sustain the heavy to very heavy rainfall. 

Sustained rains over have helped the rainfall deficits to moderate to 25 per cent over Himachal Pradesh and 50 per cent over the Union Territory of Jammu & Kashmir. But its cousin Ladakh is an exception where the deficit has worsened to 68 per cent. The other significant deficit is in North-East India over Manipur (-47 per cent).

Mostly normal/above-normal

Of the 37 States and Union Territories, 32 have received normal or above normal rainfall till date. Of the eight States/Union Territories in the South, five are in 'excess' category while two are comfortably 'normal' with Kerala (-2 per cent) being an exception. No major rain is indicated for the South during the rest of August.

On Sunday afternoon, the heavy rain belt resembled capital 'C', starting from the heavily clouded Jharkhand to Chhattisgarh, Central Maharashtra, North Interior and Coastal Karnataka before curving back to Interior Peninsula from Mangaluru into Bengaluru and later Chennai and adjoining South-West Bay of Bengal.

Ideal conditions for monsoon

Given the ideal settings in the North, the IMD sees an increase in rainfall over North-West India from Tuesday with fairly widespread to extensive rainfall over the plains as well as Uttarakhand in the hills from Tuesday to Thursday.

Extremely heavy falls are forecast over West Rajasthan and Uttarakhand on Tuesday and over North Punjab on Wednesday. In the South, widespread rainfall with isolated extremely heavy falls were forecast for Telangana, Konkan, Goa, Vidarbha and Chhattisgarh on Sunday.

Rainfall outlook for Monday.

A similar forecast is valid for the Ghats of Madhya Maharashtra and Gujarat until Monday. The likely formation of a new low-pressure area in the Bay will bring back reasonably widespread to extensive rainfall with isolated heavy to very heavy falls likely over Odisha and the plains of West Bengal on Tuesday and Wednesday.

Another low in making?

Formation of the new low over the Bay may bring fairly widespread to widespread rainfall with isolated heavy to very heavy falls to Odisha and pains of West Bengal on Tuesday and Wednesday. Moderate to severe thunderstorms accompanied with lightning may lash South-West Uttar Pradesh, Central and East Rajasthan, Uttarakhand, Chhattisgarh, South Jharkhand, Telangana, Rayalaseema, Coastal Andhra Pradesh till Monday.

Projections by the European Centre for Medium-Range Weather Forecasts suggest that yet another low-pressure area (fifth in the August 2020 series) would form in the Bay of Bengal before the month is out. This low might be triggered over the Head Bay (West Bengal-Bangladesh) region by August 25 and wrap up an active monsoon run with a likely surplus rainfall record.

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