Weather Vane. Monsoon in withdrawal mode

The south-west monsoon has started withdrawing from the western parts of Rajasthan, and it looks like the process is set to gather steam.

The monsoon could retreat rapidly from north-west India to east India and adjoining central India, starting this week.

The overall deficit looks set to beat the forecasts of even the pessimistic India Met Department, which must be credited for proving a point by sticking to its dire long-range forecasts made early in the season (for a 12 per cent deficit). The forecast was challenged by political and bureaucratic lobbies, and faced resistance from the corporate sector which reportedly wanted the forecasts to be ‘sexed up’ so that economic decisions could be influenced.

Accurate forecast The Met is ‘relieved to have been proved correct’ but worried over the impact the mounting rain deficit could have on the farm economy, sources said. It is now going back to the drawing board to find how its forecasts for the entire season will pan out, with the rain deficit already sizeable, with one month to go for the withdrawal process.

The withdrawal begins from the western parts of Rajasthan but can be interrupted by residual moisture transported across the border from the extreme west and north-west (Rajasthan and Gujarat) by incoming western disturbances. In the south, the resistance comes from moisture lingering over the Bay of Bengal and shifting into peninsular India. 

Though propagating fast over the north-west, east and central India, the withdrawal process can be blocked over peninsular India where late showers of varying intensity are forecast over the next two weeks.   

Deficit theme Meanwhile, the Met update said that the last two weeks saw rain deficits of 37 per cent for August 20 to 26 and 17 per cent for August 27 to September 2.

The overall deficit for the country as a whole until September 4 is 13 per cent, which is slightly worse than the 12 per cent deficit that the Met had assessed in advance.

But the Met can rightfully claim brownie points for forecasting a deficit monsoon this year and sticking to it.

A status update and outlook statement in the form of an Extended Range Weather Forecast by the Met in association with the Indian Institute of Tropical Meteorology, Pune, and the Indian Council of Agriculture Facility in Hyderabad stated that the last two weeks saw normal or above normal rainfall over east and north-east India.

Normal or above normal rainfall occurred in either of the last two weeks in the east and parts of the south —  Jharkhand, Gangetic West Bengal, Odisha, Chhattisgarh, Vidarbha, South Interior Karnataka, Rayalaseema and Tamil Nadu.

Below normal rainfall occurred in the last two weeks over north-west India, central India and large parts of the south.  

Over the next two weeks, the monsoon is forecast to withdraw from north-west India, east India and central India. Normal or above normal rainfall over east and north-east India and south peninsula is forecast in this phase.

Normal or above-normal rainfall would occur in either of the next two weeks in Nagaland, Manipur, Mizoram, Tripura, Konkan, Goa, Madhya Maharashtra and Vidarbha. Below normal rainfall could occur over north-west India, west India and central India.

Moisture stress As for crops, even though moisture stress had impacted regions such as Rayalaseema until the first fortnight of August due to deficient rainfall, the situation has since improved.

However, Marathwada, north-interior Karnataka, Telangana, Madhya Maharashtra, Gujarat State and Uttar Pradesh are still experiencing moisture stress. There have been reports of floods in some districts of Assam and in Gangetic West Bengal in August.

North-west India will be very dry (large negative departure from normal rainfall) and western parts of central India will also be deficient during September 4-10.

The rain belt will be mainly over eastern parts of the country and southern peninsula.   During the subsequent week (September 11 to 17), an almost similar pattern of rain is forecast to prevail.  

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