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Monsoon third-best in 30 years despite a truant July, says IMD

Vinson Kurian Thiruvananthapuram | Updated on October 01, 2020 Published on October 01, 2020

All-India seasonal rainfall this year at 109 per cent of the long-period average (LPA) has been the third-highest in the last 30 years after 112 per cent in 1994 and 110 per cent in 2019, as per the salient features of season brought out by the India Meteorological Department (IMD)on Thursday.

In the process, 2019 and 2020 also became two consecutive years with above normal monsoon rainfall after 1958 (110 per cent) and 1959 (114 per cent). The highlight of this year’s bountiful rainfall was achieved despite a deficit in July, normally the rainiest month.

Unfavourable July signals

The IMD said that July witnessed many unfavorable features resulting in deficient rainfall for the country as a whole (10 per cent). It attributed this lackadaisical performance during the month to the absence of any major disturbance (low-pressure area/depression) over the Bay of Bengal.

Absence of such major weather-making systems had also compromised the health of the monsoon trough, its very backbone over North India, during July. The trough lay to the north of the normal position or close to the foothills of the Himalayas on many days, sign of a weak monsoon.

But, as would normally result from proximity to the trough, North-Eastern States, Bihar and adjoining East Uttar Pradesh were subjected to frequent and prolonged floods during this phase. At the same time, major parts of Central and North-West India received deficient rainfall.

Drastic reversal in August

This position was reversed drastically in August with the country getting excess rain across the four weeks with 13-41 per cent above LPA during week ending August 12 to the week ending on September 2. Most deficient monsoon conditions were confined to the second fortnight of July.

 

In effect, August witnessed rainfall at 127 per cent of the LPA, highest in 44 years after August 1976 (128.4 per cent). It is also fourth highest in last 120 years. The highest ever percentage departure for the month of August during 1901-2020 has been 33 per cent above LPA in 1926.

In hindsight, the IMD underestimated the actual rainfall over Central India (115 per cent against predicted 103 per cent), North-East India (107 per cent against 96 per cent) and South Peninsula (129 per cent against predicted 102 per cent) while it overestimated the forecast for North-West India (actual84 per cent against predicted 107 per cent).

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Published on October 01, 2020
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