India’s monsoon rainfall, already 7% more than what is normal, has started to withdraw, with the India Meteorological Department (IMD) saying that the system had begun retreating from parts of southwest Rajasthan and Kutch on Tuesday.
The ‘normal’ or average date of withdrawal from southwest Rajasthan was September 17. The withdrawal of the Southwest monsoon was based on meteorological conditions such as anti-cyclonic circulation (dry air that is the opposite of a cyclone), the absence of rainfall in the last five days and water vapour imagery indicating dry weather conditions over the region.
The monsoon withdrawal is a long drawn process and extends into mid-October though the IMD considers September 30 to be the final day of monsoon rain over India. The rain after that is categorised as ‘post monsoon’ rainfall.
September rainfall so far has been 11% more than rainfall, following a trend in recent years that is seeing excess of rainfall in a month that marks the waning of the four-month monsoon. Most of the rains however have been in the southern peninsula and central India, that has seen 29% and 33% more rain than what is usual for these regions in September.
India has so far recorded 7% more rain than what is normal for June 1 – September 20. The surplus is due to excess rain in central and south India. The northwest, eastern and northeastern parts of the country have registered a deficit of 4-17% of their normal rainfall.
Despite excess rainfall, large parts of Uttar Pradesh, Bihar, Jharkhand, Manipur, Tripura and West Bengal have reported deficient rains, affecting the rice crop this kharif season.
M. Mohapatra, Director-General, IMD said last month that the rainfall average for the country as a whole was likely to be above normal, at approximately 109% of the long period average of 167.9 mm for September.
