The Monsoon trough during the Monsoon season gets established only towards the end of June or beginning of July when Southwest Monsoon covers the entire country. In regard to its normal position, the trough runs across the Indo Gangetic Plains up to the Bay of Bengal.
The trough happens to be a very important feature and controls half of the Monsoon rains across the country in virtue of its position. The trough has an oscillating nature and shifts north or south of its normal position due to either Monsoon systems moving from Bay of Bengal to central parts of the country or due to the Western Disturbances in the Western Himalayas.
Currently, the Monsoon trough is running south of its normal position because of the low pressure area which is over Madhya Pradesh and its adjoining areas. Currently, the trough is passing through Bikaner, Sawai Madhopur, Shivpuri, centre of low pressure area, Pendra, Bhubaneswar and towards the Bay of Bengal.
The combination of the trough and the low pressure area has caused widespread rainfall activity over the states of Odisha, Chhattisgarh, Telangana, Madhya Pradesh and even Rajasthan during the last 48 hours.
With the low pressure area becoming less marked and ultimately getting filled up. This trough may not move up entirely as the two ends have different movements.
Thus, the western end may shift up as a Western Disturbance is the upper regions, which will help it move and it will even go beyond Delhi NCR before ultimately shifting along the foothills. Thus, Delhi and the NCR region may see some rainfall activity tomorrow.
In fact, after 24 hours, the foothills of Himalayas including the cities of Jammu, Dharamsala, Nainital, Katra, Dehradun, Haridwar, Shimla, Pathankot, Hoshiarpur and Chandigarh. Thus, these rain activities will continue for some time over these areas at least.
The eastern end will take a little longer to shift upward but will eventually move towards the North. After 48 hours, the trough will run through its normal position and give good rains over Jharkhand, Chhattisgarh, Uttar Pradesh, and Bihar for the next three days at least.
A low pressure area may form next week which will once again cause a shift of both ends of the trough southward again.
Image Credit: wikipedia
Please Note: Any information picked from here must be attributed to skymetweather.com