During the period of 26July, the monsoon over major parts of the country, particularly over the west coast and peninsular India, was in its active phase.
A low-pressure area formed over north Bay of Bengal off Gangetic West Bengal and Orissa coast on 24 July.
There was strong cross-equatorial flow. As the system moved westward, the low-level jet gained strength and strong westerly winds lashed the north Konkan and Goa coasts. This resulted in widespread heavy rainfall over these regions.
It was "a cloudburst," a phenomenon in which there is very heavy rainfall, though for a brief period. But this was "an unusual cloudburst lasting close to 24 hours" which has bewildered weathermen.
The type of storm we saw on July 26 had very small dimension of 25-30 km. And that could be termed under the category of what we call cloudburst. It could be termed as cloudburst because particularly after 14:30 IST, received very intense showers accompanied with thunderstorm. This clearly shows this was some kind of very violent.
But it was a very unusual kind of cloudburst. Cloudbursts generally do not have that prolonged longevity. They are very short-lived. Whereas in this case, the phenomenon was noticed for 12-18 hours… the intense rainfall. Therefore it was a unique type of cloudburst.
All the ingredients that we see in a cloudburst were available there on that day. It was very highly localized.
Main Causes of Floods Siltation of drains/ nallas Siltation of drains/ nallas Obstructions of utilities Obstructions of utilities No access for desilting Dilapidated drains Slums along outfalls Increase in runoff coefficient Garbage dumping in SWDs/ Nallas mainly in slums Loss of holding ponds Encroachment along nallas Level of outfalls Low ground levels Low ground levels Suburbs City
Above picture is courtesy Mid-day. Text goes "Lying in wait: More than, 1,000 outstation commuters slept at the Chhatrapati Shivaji Terminus last night, as several trains on the Konkan route were delayed due to the rainfall. Many local train commuters who missed the last train also spent the night at the station."