With the moving of the W.D. towards the east from Kashmir and the plains of N.India,the last of the strong effective W.D. of the season seems to have passed.On 22nd.March,the plains of Punjab and Haryana had thundershowers while Delhi had some rain and the hills snow..A mild cold spell follows this system,for a day,upto 25th.March.
A W.D. is effective as long as the winter deep trough in the Pakistan/N.India region stays put,generally throughout winter.This then gives way to a high pressure region in the North,as a result of which,appraoching W.D's meeting with this "high" generally do not gain strenght.As a result,the temperatures start rising,and the "Heat low"is formed.say,about 20-25 days after intense heat.Finally,in May,this "Heat Low"stretches from Arabia to Central India.
This "heat low"is the main attraction and puller of the Monsoon and has to be well formed.
So,with the interior parts of India and Pakistan slated to heat up from end March,the required "Heat low" should start building up ,and on the other front, the waters of the Bay of Bengal can get the required heat to form the first pre monsoon low around the 20th.of April.
If this moves as per the scheduled sequence,the monsoon can be on time this year.