Monsoon to cover entire country after July 10 this year
Representative photo: iStock. The southwest monsoon is expected to cover the entire country only after July 10, 2023, according to the Indian Institute of Tropical Meteorology (IITM).
Calculations based on IITM’s forecast suggest it will take the monsoon at least 33 days to cover the whole of India since its onset in Kerala on June 8, 2023.
Down To Earth analysed the monsoon progression for this century. The analysis has revealed some interesting facts about its progression over the country. The year 2002 saw a significant stalling in the progression of the monsoon winds following its onset.
As seen in the graphic, it took 79 days for the monsoon to progress across the country in 2002, even though the onset was early — May 29, 2002. Normally monsoonal rains set foot in India on June 1.
After 2002, data suggests the 2006 monsoon season also experienced significant stalling as it took 60 days from its early onset date of May 26 to finally cover the rest of India on July 24.
The earliest progression in the last 23 years was in 2013 when it took only 16 days to cover the whole of India after making onset in Kerala on July 1.
The analysis also suggested that, on average, since 2000, it has taken over 38 days for the southwest monsoon to progress across the country, even though no coherent pattern can be observed from the data.
On being asked if the progression is arbitrary, Akshay Deoras, a climate scientist at the University of Reading, UK, told DTE:
The progression of the monsoon in India is a classic tug-of-war between dry mid-level summer air from the northwest and moist low-level monsoon air from the Indian Ocean.
The monsoon advances only when monsoon winds moisten the dry air over a region from below. Thus, the monsoon’s progression stalls if these dry winds are strong and monsoon winds are weak (or don’t carry enough moisture). So the monsoon’s progression is never a smooth and steady process that would initiate and terminate without any hiatuses, he said.
Deoras also pointed out the reasons behind the significant stalling in the progression of the monsoon in 2002 and 2006.
“Three distinct hiatuses were observed in this period (2002). The monsoon had reached eastern Rajasthan around July 20, but a hiatus was observed between July 20 and August 14 that prevented it from reaching western Rajasthan. The hiatuses were mainly attributed to stationary upper-level wind patterns,” Deoras said.
In 2006, according to Deoras, there was a significant hiatus of 15 days during June 7-22, which was mostly caused by a dry air intrusion event. Two hiatuses were observed during July, which were related to the monsoon’s intraseasonal variability or active or break phases.
In the active phase, rainfall is above average in the central parts of the country, while it is scant in northern and southern India.
As for 2013, a monsoon low-pressure system over the country during June 12-17 played an important role in speeding up the monsoon’s progression.
“This low-pressure system formed over the head of the Bay of Bengal and then travelled up to Rajasthan and Haryana, which helped in eroding the dry summer air,” he said.
He expects a low-pressure system to accelerate the progression in eastern and central India this season.
Deoras told DTE:
A low-pressure monsoon system will form over the head of the Bay of Bengal around June 25, and it will help speed up the monsoon’s progression between eastern and central parts of India. It will help erode the dry air, but a strong dry-air intrusion from Pakistan during June end will likely prevent the monsoon from reaching western Rajasthan before July 5.
DTE has been tracking the progress of the monsoon ever since the rain-bearing southwest monsoon winds were tracked around the equator, and since then, it has been a stop-start trajectory for monsoon 2023.
While the monsoon reached the Bay of Bengal by mid-way, Typhoon Mawar ensured the stalling of the winds, and there was no advancement from May 19 to May 29, 2023. Since then, the monsoon made steady progress even though it was weak before the current stalling phase began, which is expected to stretch through June 23, 2023.
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