About the System in the West:

A haphhazard low seems to be in the forming at sea level and at 850 hpa, in the south Arabian Sea. This is evident from the IMD maps shown.

And, at sea level, it seems to be propogating itself to a certain extent. Now, as the sea waters are not very "helpfull" in developing a full fledged system, this can still organise itself, to some level, and bring rain along the southern half of India's western coast.

As said in my last blog, I think Goa and Coastal Karnataka will see the rains sometime from Tuesday, 29th, and then we should see the rain patch creeping in into interior Karnataka and south interior Maharashtra.

 So, for Karnataka, its some rainfrom Monday,and some light rains for Bangalore.

For Pune it will be light rain on Tuesday.
Mumbai, as mentioned, partly cloudy Monday with light rain in some parts on Tuesday.