In a very sudden development, an UAC formed overnite over Eastern Maharashtra, and became well marked at 500 hpa. As nt, our reader pointed out correctly, it was sudden and unexpected.
During the night, I monitored the cloud mass, and observed it moving westwards. At 9.30, saw it approaching Mumbai at "super speed". A 4.30 IST rain map shows its proximity to Mumbai at that hour.
Cloud tops are at -50c, and could form 2 level thunder clouds.
A sudden burst of rain became inevitable for Mumbai.
All forecasts thrown away ! No model could forecast this rain spell !
As, we do not know when an unexpected guest will leave, unlike a planned guest who tells us his programme, we do not know the duration of this spell.