The arrival of monsoon is always preceded by pre-monsoon showers and the activity lasts for a few days. Delhi has been witnessing a change of winds for the last about 3 days. The heat wave has abated and some pockets experienced light rain and showers. These are precursors to the monsoon arrival. Delhi/NCR was lashed with moderate showers, today morning. These showers were more intense over the northern region of NCR. The airport observatory, Palam was raided with sharp showers measuring 16mm of rainfall till 8.30 a.m. today morning. Noida, Greater Noida and Bulandshahar also witnessed decent showers lasting for over an hour. The record observatory at Safdarjung registered a trace of rainfall.
There is a cyclonic circulation over northwest Rajasthan and another one over northeast Rajasthan, southwest Uttar Pradesh and the Delhi region in the lower levels. An east-west trough joining these features is running in very close proximity of Delhi, triggering the pre-monsoon showers over and around Delhi. A well-marked cyclonic circulation is also marked over the northwest Bay of Bengal (BoB), off the Odisha coast. This is likely to move inland tomorrow over parts of Odisha, Jharkhand and West Bengal. The east-west trough is likely to extend and join this circulation, as well. The movement of BoB circulation will strengthen the easterly flow all along the Indo-Gangetic plains. The circulation around Delhi region will get more organized with sharp outlines, in the next 24 hours.
The cyclonic circulation around Delhi/NCR will persist for at least 48 hours. Under the influence of east-west troughs and this cyclonic circulation, Delhi and its suburbs are likely to have heavy rain and thundershower activity on the weekend, of 29th and 30thJune. Low-lying areas may get flooded and roads and streets may get waterlogged during this time. Gusty winds, lightning strikes and loud peals of thunder will usher the southwest monsoon over the national capital, most likely on 29thJune. Monsoon showers will keep lashing the city and suburbs, albeit with less intensity, from 01stJuly onward. This may continue for nearly one week, providing much-needed relief from the heat to Delhiites.
