National

August rain exceeds forecast

A view of a collapsed bridge on Wainganga river following heavy rains, in MP's Seoni district.   | Photo Credit: PTI

August rainfall has been nearly 26% more than what is normal for the month. On July 31, the India Meteorological Department (IMD), as part of its monthly update to the monsoon forecast, said that August — usually the second rainiest month after July — rains would actually be 3% lower than usual.

Also read | August receives 25% more rainfall; highest in 44 years: IMD

However, India ended up with 327 mm of rain in August instead of the normal 258 mm.

This was largely due to torrential rain in central India, which has received nearly 495 mm rain instead of the regular 307 mm — a 61% surplus. The southern States together have also received 35% more rain — 256 mm instead of the regular 188 mm.

The net result of a munificent August has been that overall monsoon rainfall from June 1-August 31, or the monsoon season so far, has been 9.8% more than normal. In its most recent update, the IMD had said that it expected the monsoon to be 104% of the Long Period Average of what is normal for the second half of the season.

Also read | India to receive normal monsoon, forecasts IMD

A senior IMD official admitted that August rainfall was well outside the IMD’s forecast window. “August has been exceptional for a few reasons. There were nearly five rain-bearing low pressure systems that formed in the Bay of Bengal and brought a lot of rain to central India and even beyond to north and northwest India. Secondly, the cool conditions in the Central Equatorial Pacific are also favourable for monsoon,” Mrutunjay Mohapatra, Director-General, IMD, told The Hindu.

The occurrence of such systems could not be forecast 7-10 days in advance. “These are called intra-seasonal variations. And we have been issuing warnings on their occurrences and the likelihood of heavy rains,” he added.

The IMD is expected to issue a monthly update on the monsoon later this week for September, the last monsoon month and responsible for about 17% of the total monsoon quota of 88 cm.

Also read | Unhappy with IMD, Kerala tests private forecasts

In July too, the IMD’s estimate was off the mark. On June 1, it forecast rains in that month to be 103% of its normal. India ended up with a shortfall of 9.7% mainly due to central India and northwest India registering shortfalls of as much as 25%. However, excess rains in June meant that the July rain deficit was partially offset.

The IMD’s monthly forecasts have an inbuilt error window of 9%. But both the August and July forecasts fell outside their margins.

Increasingly erratic rainfall is a hallmark of climate change’s effects on India. The Ministry of Earth Sciences had earlier this year released India’s first official study on climate change. It said that though the monsoon is on track this year, increased warming would result in more erratic rainfall patterns, recurrent cyclones and more volatile storm surges, droughts, heat waves and floods, making these events more frequent, intense and less predictable.


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Printable version | Aug 2, 2021 3:52:58 PM | https://www.thehindu.com/news/national/imd-forecast-fails-to-forecast-excess-august-rains/article32489406.ece

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