Last night's low-pressure area over coastal Bangladesh is in the process of crossing over the international boundary with a portion lying over West Bengal this morning.
It continued to hold into position the trough that runs into it from Punjab cutting across across Haryana, Uttar Pradesh, Bihar and Jharkhand.
Ideally, the 'low' should be located in the Head Bay with the southeast end of trough dipping into the Bay waters.
This position allows the 'low' to feed in the winds and moisture into the trough towards the trough.
The winds would transport the moisture deeper northwestward into Uttar Pradesh, Haryana, Punjab and Rajasthan, where the other end of the trough would be located.
Heavy rain
But this alignment of the 'low' has not materialised, and instead, it is pulling in whatever moisture it can from its current location over land.
The Met Department has forecast heavy to very heavy rain for Assam, Meghalaya, foothills of West Bengal and Sikkim for today.
Heavy rain is also likely over Jharkhand, Chhattisgarh, Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura in East India and Konkan, Goa, Coastal Karnataka and Kerala on the West Coast.
Hazy in Kolkata
It is currently hazy over Kolkata with a thunderstorm forecast to break out later in the day.
At Midnapore, it is raining currently while Jamshedpur witnessed a thunderstorm earlier in the day.