Monsoon withdrawal might be staggered and slower this year, says IMD

IMD accepted that actual rainfall in July and August was outside its forecast as the spread of low-pressure areas was uneven, though the total quantum was lower than last year

After pounding the country with surplus rain in August, the southwest monsoon will not go away in a hurry. 

Though the withdrawal may start from western Rajasthan – from the second week of this month – rain may continue in other parts of India.

According to the India Meteorological Department (IMD), this is due to the emergence of fresh low-pressure areas (LPAs) over the Bay of Bengal. They will cause fairly widespread rain over the western parts of India. This will slow down the process of monsoon’s withdrawal from India.

Usually, the southwest monsoon starts withdrawing from western Rajasthan from September 17 and the process is completed by mid-October. 

However, this year, the IMD said though it may start withdrawal from the middle of September, it may not be smooth. This is because fresh LPAs are building, and these will cause more rain.

The Met department also expects the season-end cumulative southwest monsoon for 2020 to be more than its forecast of 102 percent of the long period average, as rains are continuing over several parts of the country. However, it will be less than 110 percent of the long period average and might fall in the normal to above-normal category.

“Withdrawal of monsoon may begin from the western parts of Rajasthan in the week ending September 18. But we are also expecting an LPA to develop over the west-central Bay of Bengal around that time. While withdrawal of monsoon may begin, we are still studying as to when it’s likely to completely withdraw,” Mritunjay Mohapatra, director-general of the IMD told reporters on Monday.

A staggered and delayed withdrawal of monsoon, particularly over the rainfed areas of central and western India, may aid planting of the upcoming rabi crops.

At the same, if the residual rain is excess, then it may cause extensive damage to the standing kharif crops, particularly those which have been planted late.

The IMD said the new LPA will cause heavy rain over Maharashtra, Karnataka and Kerala in the next four weeks.

“The country is likely to see normal to above normal rainfall in September, though in the second week of September, monsoon rain is likely to be deficient in most parts of the country, including northwest and central India. But it is likely to resume after September 17,” Mohapatra added.

The IMD said actual rainfall in July and August was outside its forecast as the frequency of LPAs was uneven though their total number were less than last year.

As against the average 13-14 LPAs, India experienced around 7 LPAs this year, several of them coming in August.

This year, the southwest monsoon was 17 per cent above normal in June, while in July it was 10 per cent below normal. However, the rains recovered sharply and the cumulative rain was 27 per cent above normal in August. In August, around 27 days had seen LPAs. The total amount of rain in August 2020 across India was the one highest for the month since 1926.

As on date, out of the 36 meteorological subdivisions in the country, only three have received deficient rains.

Till September 6, the southwest monsoon has been cumulatively 107 per cent of the long period average, which, in other words, means 7 per cent more than normal.

The long period average of the four-month southwest monsoon season is around 88 cm.

Private weather forecasting agency, Skymet, on Monday, also said the southwest monsoon is expected to withdraw from west Rajasthan shortly.

The monsoon entered India on June 1 this year and covered the entire country by June 26, almost 12 days ahead of its normal schedule.

The healthy progress of the southwest monsoon this year has boosted sowing of kharif crops, which till last week reached an all-time high of over 109 million hectares. Oilseeds and rice led the way.