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IMD forecasts normal rainfall in August

The India Meteorological Department has said that monsoon rainfall in August, the second rainiest of the monsoon months, will be “normal” as would be the rainfall in August and September.

Normal in the IMD parlance implies a 5% window of error. The normal amount of rainfall during August is 25.8 cm, whereas during August and September it is around 42.83 cm.

The updated forecast, however, warns that “below normal to normal rainfall” was likely over many areas of central India and some areas over northwest India. Most parts of peninsula and northeast India are like to register normal rainfall.

So far, cumulative monsoon rainfall from June 1 to August is 46.5 cm, or about 1% less than the 47 cm expected during this period. Though rainfall in the second half of June and first half of July was weak, there was a pick up since the 15th of last month which led to the deficit being overcome.

A forecast for a “normal” August is predicated on the sea surface temperatures (SST) and atmospheric conditions over the equatorial Pacific Ocean expected to remain at a tepid “neutral” level. However, the IMD said, the SSTs over central and east equatorial Pacific Ocean was showing a “cooling tendency” because of which there be more rainfall.

Other global factors that influence the monsoon are the sea surface temperatures over the the Indian Ocean. “Currently, negative Indian Ocean Dipole (IOD) conditions are prevailing over the equatorial Indian Ocean. The latest forecasts indicate that negative IOD conditions are likely to continue during the remaining part of the monsoon season,” their statement noted. The IOD refers to a cyclical swing in temperatures, with a “positive” IOD generally associated with increase rainfall.

So far, the rainfall in aggregate has been fairly well distributed over India. Northwest India has seen a 1% increase from what is normal. Central India has got exactly the expected average rainfall, and while the northeast has registered a 13% decline, compensated by a high base rainfall, the Southern Peninsula has received 13% more rainfall.


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Printable version | Sep 22, 2021 8:01:21 AM | https://www.thehindu.com/news/national/rainfall-during-august-and-september-likely-to-be-on-higher-side-of-normal-imd/article35678052.ece

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