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Salient weather features over the country for the month of Oct, 2020: IMD Report

1.       Southwest Monsoon withdrew from the entire country and Northeast Monsoon rains simultaneously commenced over extreme south peninsular India on 28th October 2020. Past dates of withdrawal of southwest monsoon from entire India since 1975 shows that withdrawal from entire India was most delayed during 2010 (29th Oct, 2010) followed by 2016 and 2020 ( 28th Oct).

2.       Among all the months, both October and November are the most vulnerable months of Cyclonic disturbances (Depressions +Cyclones) formation over the north India Ocean (NIO). The average frequencies Cyclonic disturbances as depressions and cyclones are 2.0 and 1.8 during October and 1.8 and 1.2 during November respectively based on data of 1961-2019.  However, in Oct 2020, a total of 3 Depressions formed over NIO with one intensifying into a Cyclone.  Out of these 3 systems (1 Deep Depression & 2 Depressions) formed over NIO, 1 formed over the Arabian Sea and 2 (one Deep Depression & one Depression) formed over the Bay of Bengal. Date since 1980 shows that there were no cyclones in October during 14 years out of last 41-years.   During October 2020, the genesis, intensification, movement and landfall characteristics of all the three systems along with expected duration were well predicted by IMD with sufficient lead time.

3.       During, Oct, 2020, the rainfall over the country is 78.1 mm with 3% above Long Period Average (LPA) over the country as a whole.

4.       October is the transitional month of temperature when variation of both maximum and minimum temperature is monitored for providing guidance to various users. Fig 6 shows observed spatial temperature pattern of monthly average minimum, average maximum and mean temperature over India and their departure from normal for Oct 2020. Fig 7 shows time series of All India monthly average minimum, average maximum and mean temperature during 1971-2020. The mean maximum, minimum and average temperature for the country as a whole during Oct 2020 was 21.90 º C, 32.0 º C and 27.0 º C respectively. The month of Oct 2020 was the warmest night temperature in record since 1971(i.e. in last 50-years) and was 3rd warmest, in terms of average monthly maximum and mean temperature since 1971 for October month, with 2015 as the warmest  followed by 2017 for the month.     Fig 8 shows time series of Northwest India monthly average minimum, average maximum and mean temperature during 1971-2020. The mean maximum, minimum and average temperature  over Northwest India as a whole during Oct 2020 was 16.43 º C, 31.07 º C and 24.15 º C respectively. The month of Oct 2020 was 19th in the rank of the warmest night temperature in record since 1971 and was 3rd warmest, in terms of average monthly maximum and mean temperature since 1971 for October month, with 2017 as the warmest followed by 2010 for the month. The average mean monthly temperature of Oct 2020 is 6th warmest in the rank with 2017 as the warmest followed by 2016 for the month. However the national capital region and adjoining areas of Haryana, Punjab, Uttar Pradesh & Rajasthan recorded lower temperature during Oct. 2020. Temperatures records over New Delhi (Safdarjung) for the month of Oct 2020 and comparison with data since 1951 shows that it recorded lowest monthly mean minimum temperature (MMT) during Oct. 2020 (17.2 º C) after Oct. 1962 (16.9 º C) (Fig 9)

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