Southwest Monsoon season 2022, with the longevity of four months is now entering the closing month of September. More familiarly, it is denoted as the withdrawal month of Monsoon. The withdrawal process has large variability and lasts for anything between 20 to 40 days.
The commencement of withdrawal from West Rajasthan was earlier stipulated as 01st September. However, it was noticed that Monsoon withdrawal was not on time since 2006 onward. There was a variability of as much as 23 days. Accordingly, the withdrawal dates were revised, effective 2020, based on the data from 1961 to 2019.
As per new norms, the monsoon withdrawal commences from West Rajasthan on 17thSeptember. Withdrawal from various parts is now 7-14 days later than the earlier dates. Final withdrawal date from South Peninsula remains 15thOctober.
On earlier occasions, the monsoon commenced withdrawal as early as 02ndSeptember in 2005 and as late as 09th October in 2019. Last year also, the withdrawal got unduly delayed and commenced on 06thOctober. However, the process was speedy and got completed by 24th October from South India. Simultaneously, it paved the way for onset of Northeast Monsoon over Tamil Nadu.
Weather activity has largely reduced over North India in the last week or 10 days. It is giving a feel of likely withdrawal from West Rajasthan. However, the process may not start anytime soon. There are a few pre requisite conditions and criteria for commencement of withdrawal. Monsoon withdrawal as such is always retrospective. The required pattern is observed for sustenance and persistence before the formal announcement.
Major indicators remain under observation for sufficient duration. Anticyclone establishment at a level of 5000’ over Rajasthan is primary requirement. Also, the rainfall should completely cease for continuous 5 days over the region. Additionally, the moisture content in the environment need to deplete, as inferred from the water vapor satellite imageries. Over and above, the synoptic situation for any meteorological development, at least for the next 10 days need to be ascertained.
Though, there is absence of weather activity over West Rajasthan and other parts of North India, but there is a twist in these conditions likely after one week or so. While rising temperatures, shrinking humidity levels and long sunshine hours may be hinting at conditions akin to withdrawal, but the long term prognostication suggest ‘wait and watch’ for the next 10days. There is a possibility of fresh weather system emerging over Bay of Bengal in the next week. It will be little early to preempt its timing, track and intensity, at this stage. The meteorological conditions need to be observed closely at the start of September.