Saturday, June 19, 2010

125mms of Rain in 90 Minutes ! 
What Mumbai experianced on Friday afternoon was a virtual cloudburst.
I personally could not witness the rainstorm,as was in Goa,in fact waiting for the aircraft clearance at Goa airport from 3pm to 9pm. Thats till our aircraft got the go-ahaed to proceed to Mumbai.
Even though it was the aftermath of the storm,fortunately,I was able to observe the towering cumulo- nimbus thunder heads at eye-level from the airplane whilst approaching Mumbai. The route taken from Goa was initially North along the coast, but about 150kms before Mumbai, the aircraft turned towards the North-West, and flew over the sea, to approach Mumbai from the west, and it had flown a good 50-60 kms due west off Mumbai. Since the aircraft took the sea route while approaching Mumbai, I observed the maximum cumulo-nimbus clouds, thick and threatening, about 40kms off the city coast, due west.The cloud height observed then could have easily been  35000 feet above MSL, with the outside cloud temperature showing -30c on the passenger information screen. Even though it was night, a keen observer could locate and study the towering thunder heads at close quarters, infact flying through  massive storm clouds at times.

With 125mms of rain in just 90minutes, it was a massive cloudburst, and could be due to a formation of a local vortex within the off shore trough. The local heat during the day, it was 32c on Friday, added fuel, and convection pushed up the vertical cone to heights of maybe 45000 ft during the storm. Cloud tops were observed at -55c in the weather maps.

As seen in the satellite image, a vortex is seen hanging around off the North Konkan coast even today, with enhanced cloud cover.
Now, as per the forecast models, this cloud cover will remain in the same stationary position till Tuesday, off the Maharashtra coast, and on Tuesday move towards Mumbai, and precipitate heavy rain along the Mumbai-North Konkan coast on Tuesday/Wednesday.
Since there is a possibility of an active MJO enhancing Monsoon prospects along the west coast, I would prescribe to this forecast, but for this to happen, there could be some mild heating again along the "forecasted "region on Sunday/Monday.
That is when I would presume an upper air circulation to form over south Gujarat, and precipitation could resume in strenght along Saurashtra from Tuesday.
Rain is seen pushing into interior Maharshtra this weekend. Some favourable rains could be expected in Madhya Maharashtra, Marathwada and Vidharbh this weekend.

The Bay seems to remain devoid of a low till Tuesdat at least. The East-West trough is seen along the plains of North and Northeast India, but bluntly cutting off in the east. Hence local pulses will bring rains along the Orissa/West Bengal coast this weekend , and at least till Tuesday, I do not see any meaningful rain in T.N. and A.P.
As per the 200 hpa jet streams, I would still stay put the Monsoon at 22N. After,the 23rd, when the active MJO gets into action, we could expect a further advance of the monsoon, in the eastern and western regions.Monsoon may push into U.P. and M.P.after 23rd.

Mumbai Forecast: 
Mumbai Colaba has recieved 478mms of rain in the 18 days of this month. This is much better than the 266mms recieved in the whole of June last year. A good and bountiful beginning for a thirsty city.
Santa Cruz has recieved 333mms of rain till date this month, against 216mms recieved in June last year.
I see a slight let up in the rains for the weekend, say about 20-25mms per day, with with a chance of a thunder shower in some areas. Day temperature may go up to 32c on Sunday.
Rainfall will increase from Tuesday,22nd, thru Wednesday23rd. For Tuesday/Wednesday, I would put the accumalated rainfall at 120/150mms. Again,check up local areas for flooding on Wednesday,23rd.

If you would like to estimate in the poll, the overall India performance of the Monsoon till 16th. June is at -5%.


emkay said...

great to here u had a first hand view of the cloud top. Indeed sitting at Fort around 1730, had given up hope of reaching home by train. At 1700 hrs it was pitch dark in that area and the clouds too dark !! Was indeed scary. Relieved to see normalcy return by 1900 hrs.

Anonymous said...

I agree with Emkay. I was at my Andheri office and it poured for around 40 mins there. My office is in a lane and the there was water logging till ankle length.

Honestly not seen so much lightning and thunder in the June period (was looking more like Sept - Oct type storm)

Minimum Temperatures in NW India on 9th Morning; Punjab : Adampur 5.2c, Faridkot 5.5cBhatinda 6.0c,  Amritsar 6.8c, Gurdaspur 7.7c Rajasthan...