Southwest monsoon is on time, heat waves delay progress in east India: IMD official

Significantly higher-than-normal temperatures recorded in large swathes of northwestern and eastern India the past three days have slightly slowed down the monsoon’s progress, an India Meteorological Department official said. 

The onset of monsoon showers is expected in eastern India this week, IMD scientist Soma Sen Roy told Mint. As per the department’s forecast on Wednesday, the monsoon is likely to advance into more parts of Odisha, Chhattisgarh and Maharashtra. The onset date for Delhi is 30 June, and 5 July or after for Rajasthan. 

This assumes significance as the southwest monsoon brings nearly 70% of the rain India needs for its farms and to refill reservoirs and aquifers.

Timely arrival of the monsoon is crucial for India’s agricultural sector, considering that around 56% of the net cultivated area and 44% of food production depend on monsoon rainfall. Normal precipitation is imperative for robust crop production, maintaining stable food prices, especially for vegetables, and bolstering growth.

Agriculture contributes about 14% to India’s gross domestic product, underscoring the importance of a favourable monsoon for economic growth.

“Climatologically, normal monsoon onset dates for eastern India—Bengal, eastern Bihar, eastern Jharkhand and Odisha is between 10-15 June… These are climatological dates, meaning it is never true that exactly on a particular day monsoon will be arriving in a particular city or state; it could be one or two days ahead or behind. Monsoon is advancing daily,” Roy said. 

“It’s just that monsoon does not progress at the same speed throughout the country. It is a surge, and sometimes the surge is a bit more to the west and sometimes to the east. Accordingly, the monsoon advances.”

More active in southern India

“Monsoon proceeds in surges. A surge comes and in that surge it may advance. If you look at the progress of the monsoon this year, on 1 June it advanced more quickly over Kerala but subsequently on 2 June it advanced more rapidly on the eastern side,” the IMD scientist said. 

“This is a day-to-day change that is happening. I cannot make a blank statement that monsoon is delayed or stalled. In peninsular India, monsoon is very active and progressing quicker than over east India,” Roy added.

The southwest monsoon hit the Kerala coast on 31 May, a day ahead of its normal date. Southwest monsoon rainfall over the country during June-September is likely to be 106% of the long-period average, with a model error of +/-4%.

IMD director general Mrutyunjay Mahapatra said that for the second phase of the monsoon, the forecast probability is 32% and the climatological probability is 16%.

Regarding the arrival of the monsoon in northwest India, Roy said the arrival of the rains up to central India could be on time, but weaker progress and delayed rainfall are expected thereafter. 

Heat waves to continue

Since 1 June, rainfall has been 4% lower than normal in the country, with a 53% deficiency in northwest India and 33% in east and northeast India. Southern peninsular India, meanwhile, has recorded 60% excess rain, IMD data show.

“The westerly flow is dominating over north India, because of which strong winds are blowing, and the heating is penetrating up to eastern India in the absence of western disturbances. Once the easterly flow picks up, the moisture will start to penetrate, and then we shall get monsoon,” Sen said, acknowledging that heat waves were influencing the monsoon current over east India.

“We are getting severe heat waves in Bihar, Bengal, Jharkhand and Odisha. Once the easterly flow picks up, the moisture will start to penetrate, and then we shall get monsoon,” Sen said. “We expect the flow to build up shortly, and accordingly, the monsoon advancement will happen.” 

On Wednesday, maximum temperatures were 3°C to 5°C above normal and ranged between 42°C and 46°C in many parts of Punjab, Haryana, Chandigarh, Delhi, West Rajasthan and Uttar Pradesh and in some parts of East Rajasthan, Bihar, Jharkhand, Gangetic West Bengal, Chhattisgarh and East Madhya Pradesh. 

The highest maximum temperature on Wednesday was reported at Prayagra in East Uttar Pradesh, at 47.1°C.

Heat wave to severe heat wave conditions are likely to continue over parts of northwest and east India the next four days.

Heat waves have been scorching the country since mid-April, starting in the eastern regions and gradually spreading to northwest and central India. Temperatures have averaged between 45-47°C. Heatwave conditions have prevailed over Haryana since May 17, and Madhya Pradesh and Uttar Pradesh since May 18.

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