The four-month long Monsoon season, which runs from June to September, brings 70% of the country's annual rainfall. The initial phase of Southwest Monsoon this year was dominated by an evolving El Nino.
In February, the situation seemed conducive for a poor Monsoon in India. And as we entered mid-April, these observations turned out to be more accurate. From the 21st to 25th of May, the surface temperature remained constantly at 0.6oC in equatorial Pacific. This could be attributed to poor performance of Monsoon in India with rain deficiency at 43% till 12th of July. Thereafter, conditions relaxed and rain deficiency came down to 22% by end of July as the surface temperature slipped to 0oC and even further to -1oC.
Withdrawal is generally not attempted before 1st of September and commences from extreme west Rajasthan. As Southwest Monsoon approaches the withdrawal phase from a particular region, certain conditions become prevalent- change of wind pattern, reduction in cloud cover, decrease in humidity, cessation of rain, sporadic rain and temporary rising tendency of temperatures.
Last year, the Monsoon started withdrawing from Rajasthan by 9th of September and from Himachal Pradesh, Punjab, Haryana and Gujarat by the 19th. This year, the track of the present Monsoon system seems to be suggesting a possible retreat of Southwest Monsoon. According to the latest weather update by Skymet Meteorology Division in India, this year, Southwest Monsoon is likely to withdraw from west Rajasthan anytime in the coming week.
Monsoon systems over Central India
The present Monsoon system over Central India, brought widespread light to good amounts of rain, with heavy fall in pockets, over Odisha, Chhattisgarh, Madhya Pradesh, Gujarat, south Rajasthan, north Maharashtra and Konkan & Goa in the initial three days. The well-marked low pressure area then slowed down, weakened into a cyclonic circulation and re-curved to bring rain over northwest Madhya Pradesh and adjoining Uttar Pradesh. Such systems generally have a tendency to weaken after re-curving and bring only light rain. Though rain has been widespread it hasn’t helped in bringing down the cumulative rain deficiency, sitting at 11% since the 6th of September.
This system behaved differently from the previous system, which reached the hilly states of North India and played in tandem with the Western Disturbance to bring heavy rain over the region.
The track of the present system will suggest the possible retreat of Monsoon and cessation of rain from Northwest India. Successive systems developing over the Bay of Bengal will dictate the withdrawal line of Monsoon from India. Rain will now be sporadic in nature and not help in reduction of the cumulative rain deficiency, which could show a marginal rise.
Rain will be mainly light with isolated heavy falls due to localised activities. The cumulative daily rainfall will remain less than the average rainfall of the day.
