Southwest monsoon has overshot the normal dates of commencement of withdrawal from West Rajasthan. Revised schedule stipulate start of withdrawal from the border posts by 17thSeptember. Within one week, monsoon gets slated to retreat from West Rajasthan, some parts of East Rajasthan, Punjab, Haryana, Delhi, Jammu & Kashmir and Himachal Pradesh. Despite revision of dates in 2020, delaying withdrawal by 7-14 days, the monsoon has been overstepping the new timelines as well. The earliest withdrawal in the last six years, since 2017, was last year when it commenced on 20thSeptember. The most delayed withdrawal also figures during this period. The retreat of monsoon began on 09thOctober in 2019.
Monsoon withdrawal is not attempted before 01st September, irrespective of prevailing weather conditions. Certain prerequisites need to be fulfilled before announcing start of withdrawal. These include : cessation of rainfall over the area for at least 5 consecutive days, establishment of anticyclone in the lower levels dictating reversal of winds and significant drop in the moisture levels which as such is a corollary to the anticyclone over the region. The declaration of withdrawal from a specific region, may not be construed as total absence of rains for a longer period. Rains, if any, after sufficient gap need not be considered as revival of monsoon. Such a scenario is an inbuilt characteristic of retreating monsoon.
The formation of successive low pressure areas over Bay of Bengal and their travel, deep in to parts of Madhya Pradesh, Gujarat on the outskirts of Rajasthan, has delayed the process of withdrawal this season. Presently, there is a low pressure area over Jharkhand and neighbourhood, supported by cyclonic circulation. The weather system may mover more to the north, closer to North Bihar and foothills over the next 2 days. It is unlikely to break up along the foothills and rather its remnant may travel up to West Madhya Pradesh and peripherals of East Rajasthan. There are some precursors to the anticyclone over the region by 26th-27th September, but the pattern is getting tumbled before digging deep.
Under the existing scenario, light rains are expected between 22nd and 28thSeptember, over few parts of South & East Rajasthan and Gujarat. Though, extreme western parts of Rajasthan may not get noticeable rains but moist winds may hang around these parts, longer than normal. Therefore, the withdrawal of monsoon may not commence for the next one week. Fair amount of chance for this event to roll over to the initial days of October, like it happened in 2019 & 2021.