Tuesday, September 13, 2011

A fresh low pressure has formed in the Bay. BB-7, lies off the Orissa/W.Bengal coast at 998 mb. Its an "in situ" formation, and reflects an active monsoon pulse in the axis.

Like mentioned earlier, would normally expect the system to track along the axis "corridor". The axis currently runs from the seasonal low over Central Sindh ( Pakistan), thru Jaisalmer thru eastern M.P. and then thru Orissa into BB-7. But then, one should expect the axis itself to remain in place.
Anyway, already flooded Orissa will get more rains and heavy falls in gangetic W.Bengal next 2 days.
Kolkata should see heavy rains next 12-24 hrs.

Would expect the system to move inland into M.P.bringing revived rainfall to east M.P. and Vidharbha. Thundershowers would effect Nagpur on Wednesday, 14th. Expect heavy falls due to convection, and rains up to 20-35 mms possible in some areas.

Further intensification or tracking of the system depends entirely on the "counter resistance" it gets from the West. Like I estimate, an anticyclone should form in the Central Sindh/West Rajasthan region from Friday. BB-7 future depends on the speed and strength of this development.
If it is countered by this anti cyclone at 850 mb (which will start the SWM withdrawal phase), it may not be able to survive much, but if the withdrawal process is weak, then BB-7 could be the master.
Rainfall for Konkan and Mumbai depends on this. Picture will get clear in a day or two.

A strong off shore trough brought some heavy rains in Kerala last 24 hrs. Would expect this to move a bit North into coastal Karnataka on Wednesday. Very heavy falls in coastal Karnataka and parts of Goa on Thursday.
T.N. expected to remain in status quo position.

The clouding in the Sindh region last several days is due to a UAC embedded in the seasonal low. Whether this is the remnant of BB-6 or not does not matter. The seasonal low on the western end of the monsoon trough is elongated, and surprisingly still attracting moisture, mainly due to non stop winds feeding from the Arabian Sea. rather unusual !
But now the winds have eased a bit, and even changed direction.Soon the clouds will thin out, and spread over a larger area, but with lesser rains.
Karachi got another day of rainfall on Tuesday, with almost 70 mms falling overnite.
As mentioned, would expect the rains to decrease from Wednesday, and almost cease from Thursday/Friday.I say a day more than previous mentioned as the moisture brought in the last 2 days can possibly cause some convection for another day.

Mumbai had a warmer day on Tuesday, with the high reaching 30.7c at Colaba and 31.7c at S'Cruz. A couple of showers wetted the city in the evening. S'Cruz has recorded 8 mms till 11 pm while it was 2 mms at Colaba. Dadar got 10 mms in the same period.

Wednesday/Thursday: Partly cloudy with intervals of sunny spells. A couple of showers, passing types, but day temperature will be at 30/31c. Rain amount 10-15 mms.

Rainfall could increase from Thursday night, but shall confirm that later.


NT said...

Consistent moderate to Heavy rain in Vile Parle area since the last 1 hour, at times the rain becomes very heavy. Was not expecting this kind of a prologned rain today.

svt said...

steady rain in dadar btw 10:25 to 11:20. And after stopping for while it now started raining once again at 11:50pm. Personally feel low after coming over MP will move northward & get affected by anti cyclone n weaken quickly.

Rajesh said...

NT:I think Tuesday's shower would be in line with vagaries' forecast put up on Monday.Forecast was partly cldy and sunny spells with 3/4 showers,and rain amt up to 15 mms.S'cruz got 35 mms and colaba 26 mms avgring 30 mms.
svt:IMD differs on the anti cyclone happening as it still puts up of SWM delay in retreat.If we go by vagaries' estimate, then what you say concurrs with the blog put up.

and, would not like to put up a Mumbai based poll, as readers are from all over.

NT said...

Rajesh, the NOAA data for Santacruz airport shows 'light rain with Thunder' around 12:00 AM, the time I noticed lightning and thunder in the Juhu area yesterday night. As we discussed none of the radars picked up the Lightning. Quite an interesting sudden Thunder-storm that, yesterday night.

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