Monday, June 06, 2011

Latest on AS-1:

The off shore trough running along the west coast persists, with the current system embedded in it.
The system has been puzzling one and all. A couple of days back, it had detached itself from the trough, into an independant low, a fact mentioned in Vagaries a few days back. It had moved away as much as 68E, away from the coast. Subsequently, it started moving back towards its "parent" trough, and re-merged with it.

On this development, the SWM pushed itself Northwards along the west coast, and since the AS-1 remained in the "cover" of the trough, the combined effect moved the SWM fast towards 19N.
South Gujarat cities like Bharuch, Navsari, Surat and Baroda got between 15-25 mms of pre monsoon rain.

The odd behaviour of As-1 kept various experts guessing on movement and track direction, for almost the last 8 days.

On Sunday, 5th June, AS-1, system (since a "designation" was difficult as explained), moved very close to Mumbai at 71.2E and 18.5N. Bringing in moisture and cumulo-nimbus clouds on Sunday. A mixture of convectional lightning and low rain clouds from a system (AS-1) was seen and experienced. 54 mms at S'Cruz and 27 mms at Colaba were measured.

Today, on Monday, (at 11.30 am IST), AS-1 is as per latest positioning at 18.4N and 71E, 100 kms SW of Mumbai, and at 1003 mb. Winds have geared up to 25 knts. Still is well within the trough.

The trough remaining intact, AS-1 has now all the "nourishment" to move west, and deepen a bit. The "over-staying" guest has decided (it seems) to move on -:)
And that is what (readers are commenting) Vagaries has been harping upon since the last 5 days. But, wait, if it had happened so, maybe the SWM would not have moved up so fast.

Now, this system has the SST at 30c and is showing a developing swirl, with convection at the centre, the convective bands are getting organised. Winds have swelled up to 25 knts.

Now, is the time for it to move west and deepen. Effective rainfall may just skirt the Southern most tip of Saurashtra and move away in to the sea. (Away from Mumbai).

I do not see much effect on the Sindh coast. This is because, the 200 stream line, is just above the 19N limit.

And this 200 stream at 19N, will prevent the SWM from movnig above 20N (as informed before) for the time being.

This is the synoptic position today.


Ganesh said...

Rajesh,can u please tell me what AS1 means?

emkay said...

Rajesh present position is SW of Mumbai, u mentioned SE of Mumbai.

NT said...

IMD has in it's afternoon bulletin announced the intensification of the UAC into a LOW pressure area with remarks that it will intensify further. Although (and very peculiar of them) there is no mention of the direction the LOW will take. The GFS forecasts seem to indicate that it will start it's journey Westwards only from tomorrow. Meanwhile Thundercells have developed over the Eastern horizon (yet again) and the precipitation may start in about an hour (in the northern suburbs of Mumbai)

rajesh said...

@emkay: Thanks emkay, typo error. Corrected. @Ganesh: AS-1 is the No. given by Vagaries to identify and distinguish between 2 or more systems if they come at the same time. Arabian Sea System 1'
Like we have been numbering the W.D.s.

svt said...

First time today clouds r coming from southwest or west. It doest look like we will get thunderstorm from east today. Looking at forecast very little rain is expected for next 2 days. From thursday good rains might return. AS1 might move towards iran. Is WD expected this week that might recurve system towards pak or gujarat. Too early to predict

Ron said...

so any more rains expected in mumbai..some forecast model predict rain from thursday or friday when the low pressure curves back to guj/maha region...

Anonymous said...

rain at borivali west at 8.02pm

Ganesh said...

Thanks if i understand correctly it denotes a low pressure system. But like WD stands for western disturbance,is AS also an abbreviation for something?

Anonymous said...

AS =Arabian Sea

Ganesh said...

Thanks!! :)