A land-based low-pressure area has formed over Jharkhand and neighbourhood on Monday.
This is now forecasted by a few international models to precipitate monsoon rains, initially,over central India during the rest of the week.
Model forecasts also estimate that this land based ‘low’ will take a westward course to move into central India, giving the much required rains in Chhattisgarh, north coastal Andhra Pradesh, Vidarbha, Marathwada and madhya Maharashtra.
Consequently, northwest India could also get get some rains as the westerlies along the monsoon trough interact with the easterly flows associated with the land-based ‘low’.
During this week, the system would attract moisture-laden southwesterlies winds, with rain clouds, from the Arabian Sea and is likely to commence a rain spell over western Maharashtra, north Konkan including Mumbai and south Gujarat.
But for north Konkan, and Mumbai,the inflow of substantial moisture bearing rain clouds could start "rushing into" the coastal regions from Wednessday evening itself. Heavy rains could once again start in from Wednesday /Thursday , and could, as a result of the system moving westwards,continue for the next 4/5 days..
Now, this land-based system, will be be chased by a second low from the bay, off the Orissa coast by Monday (13th. July). If true, this can make sure of that the wet spell started by the first low, continues for a further 6-7 days, in central India, as this would bring in substantial moisture from the bay. This, low, is forecasted by the IMD, and the European Centre for Medium-Range Weather.
The movement, and direction of the bay low is not forecasted or indicated by the models.
The ECMRWF also forecasts the formation of a low in the Arabian Sea by the 11th. But, this is estimated to move westwards, and "hit" the Oman coast around the 14th. as a depression.
Now, this day to day, step by step, activity and precipitation, is on the estimated and forecasted basis. I have seen, things go awry several times in the last 1 month.
Like, we have been waiting for forecasted lows from the bay for the last 21 days now. And, one suddenly shows up, un-announced. on land !
Estimates have either been delayed, by a few days, or a week, many a times this year, and I do not want to stick to fix days and dates this time. Not pessimistic, but realistic !.