Normal Monsoon In 2021 With Rainfall At 99 Per Cent Of Long Period Average, Core Agricultural Area At 106 Per Cent

The India Meteorological Department (IMD), on September 30, said that the country had received "normal" rainfall during the four-month Southwest Monsoon season from June to September.

The monsoon season officially came to an end on Thursday (Sep 30), even as widespread and heavy rain continue over different parts of the country.

IMD stated that the country witnessed a normal monsoon rainfall this year, which occurs when rainfall is within 96 per cent to 104 per cent of Long Period Average (LPA).

The 2021 all India monsoon seasonal rainfall from 1 June to 30 September has been 87.0 cm against long period average of 88.0 cm based on data of 1961-2010 (99 per cent of its LPA). Region-wise, monsoon rainfall was normal over northwest India (96 per cent) and central India (104 per cent), below normal over east and northeast India (88 per cent) and above normal over peninsular India (111 per cent).

Rainfall over the core agricultural area (monsoon core zone) was above normal at 106 per cent of LPA.

This is for the third consecutive year that the country has recorded rainfall in the normal or above normal category. Rainfall was above normal in 2019 and 2020.

In 2020, the seasonal (June-September) rainfall over the country as a whole was 109% of its Long Period Average (LPA). It was the third highest after 112% of LPA in 1994 and 110 % of LPA in 2019.

Regional Variations

IMD reported that six meteorological (met) subdivisions received deficient rainfall. These are Nagaland, Manipur, Mizoram and Tripura, Assam and Meghalaya, Arunachal Pradesh, Jammu and Kashmir and Ladakh, West Uttar Pradesh and Lakshadweep. Two met subdivisions that witnessed much higher than normal rainfall in the season are Marathawada and Telangana. Sub division wise rainfall map can be seen here, district wise rainfall map here and state wise rainfall map here.

2021 monsoon season was very uniquely placed in the historical record for its distinct and contrasting month to month variation. The rainfall over the country as a whole was 110 per cent, 93 per cent, 76 per cent and 135 per cent of LPA during June, July, August and September, respectively.

In July, the rains were slightly below normal. This was due to the absence of any major disturbance over the Bay of Bengal. During August, the presence of the unfavourable negative Indian Ocean Dipole (warmer ocean waters on the east coast of India compared to the west coast) was responsible for the deficient rainfall. In September, favourable conditions such as the weakening of the Indian Ocean Dipole ensured above normal rainfall.

Monsoon Withdrawal

The Indian Meteorological Department (IMD) also said that the prevailing weather conditions favour the withdrawal of southwest monsoon to begin from 6 October.

IMD’s models predict that due to certain atmospheric conditions over northwestern India, the region would witness a drastic reduction of moisture and absence of rainfall, leading to withdrawal of monsoon. If predictions prove right, it would be the second most delayed monsoon withdrawal that India has witnessed since 1961.

Prediction for Northeast Monsoon

The IMD also forecasted that the 2021 northeast monsoon rainfall over peninsular India is most likely to be normal (89 per cent to 111 per cent of LPA). It has also been stated that there is an increased possibility of re-emergence of the La Niña conditions during the northeast monsoon season, which would imply better monsoons.