October 31, 2021 9:50:47 pm
Kerala witnessed 589.9 mm (94 per cent surplus) rainfall in October, a figure never seen since 1901, according to data provided by the Indian Meteorological Department (IMD). Kerala recorded more rain than its October to December seasonal average of 492 mm in October alone.
Between 1901 and 2020, Kerala’s October rainfall crossed 500 mm only on three occasions — 1999 (567.9mm), 1932 (543.2mm) and 2002 (511.4mm) and not once in the last decade.
Similar rainfall trends were reported from eight other states and union territories, when October rainfall was higher than the quantum normally recorded during the post monsoon season of October to December.
At 100.7 mm, India’s October rainfall was 33 per cent above normal.
This year, Jammu and Kashmir and Uttarakhand experienced their fifth wettest October since 1901, the IMD data revealed. Last month, Jammu and Kashmir recorded 100.8 mm (182 per cent surplus) rain whereas over Uttarakhand it was 203.2 mm (476 per cent surplus).
Delayed withdrawal of the southwest monsoon was the prime reason for such large rainfall variations, especially over southern peninsular India. Cyclone Gulab and later Cyclone Shaheen also contributed to the overall rainfall during early October. The two cyclones caused significant delay in the commencement of the withdrawal from northwest India. Normally, monsoon withdraws completely by October 15 but this year, it was realised only on October 25. As a result, Kerala, Mahe, Tamil Nadu and parts of coastal Karnataka did not have a break in rainfall activity between the two monsoon seasons, thus adding to the overall monthly rainfall.
Favourable and moist conditions due to strong easterly winds and their interaction with low pressure systems in the Bay of Bengal kept the monsoon active in south India, especially over Kerala in mid-October.
Over northern India, the early arrival of strong western disturbances and their interactions with moisture-laden easterly winds brought heavy to very heavy rain over Uttarakhand, east Uttar Pradesh, Bihar, West Bengal and Odisha. It also led to early snowfall and precipitation over Jammu and Kashmir and Ladakh due to passing western disturbances.
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