Saturday, June 04, 2011

As a weak AS-1 slips out of the off shore trough, the Northern end of the trough takes on a sudden strength. We had expected the trough to remain intact no doubt, but, it is getting good moisture at the Northern end (read Mumbai), and the result is over- active convection. Huge thundercell bang on Mumbai. (See wundermap).

A heavy thunderstorm on Saturday afternoon and evening resulted in S'Cruz receiving 72 mms and Colaba 22 mms till 5.30 pm.

AS-1 however is still very weak.

In a surprise move, IMD has plunged the SWM into Maharashtra right up to Alibag and eastwards into Pune. I have calculated the advance up to Goa, and interior Karnataka. But, that's ok now, the gap is narrow. The main parameters defcient according to me, SW winds are in place (though not strong enough ), and 200 jet stream is still aligning itself, and OLR would need a northward climb. Scientists at IMD are more experienced and equipped better.

Convective pre monsoon rains in coastal Maharashtra and interiors were heavy on Friday night.(See here for link). SWM could now move up , and land up at 20N sooner than expected.


Scorching Heat to Continue across South, Houston records earliest 100 in over hundred years yesterday!...check Mark's Blog for details.


Anonymous said...

borivali (west) has only received light to moderate rain and light thunder till now. (9.21pm)

NT said...

So what now for Mumbai? Does the original forecast made by you remain in place for Sunday / Monday or would Mumbai experience heavier rains as was the situation today? Also, completely from a common man's view on the street without getting into any complex technicalities of the weather, the SWM is here in Mumbai, since what finally matters is what is the weather that is experienced on the ground. Looking at the rain data given by Rajesh in his latest blog for Santacruz - 72 mms i.e. 3 Inches and looking at the Mumbai Met's data for the rain yesterday, Santacruz has already logged around 4.5 inches of rain and there is more to come.

Rajesh said...

I think i will stick to my forecast for sunday/monday (put up on Saturday).
U think sat forecast was ok ? Quantum measured was a bit more.I mean the avg rain was around 45 mms for Mumbai. Reports from reader says hardly any rain in Borivali.

NT said...

Yes Rajesh, your forecasts for Saturday were on target. It rained around 22 mms in Colaba and as per a reader not much in Borivali (northern suburbs). While it did rain a lot in Andheri - Santacruz area that could have been due to a localized cloud. Overall I agree to your forecasts, average rain was around 40 mms. What surprises me Rajesh is the quantum of convection, as mentioned yesterday too in my comments, I was a bit surprised to see -70 degree cloud tops over Mumbai.

Rajesh said...

@NT, Evening thundershowers was forecasted for fridaysaturday, so it was ok. yes, quantum was 22 and 72, against a generalised 20 mm put up by me. Sure, it rained more, but never can tell in a thunderstorm. Lets stick to Sunday/monday forecast.
Yes, for people, rain is rain..monsoon or will be monsoonish with rough seas and more frequent rains next 2 days.,

Rajesh said...

I appreciate, that for the layman (Mumbai ), rain is rain, and not distinguished as "pre-monsoon" (as NT rightly points out).
But, one must have noticed these pre-monsoon thunderclouds rolling in from the east. Even today morning (Sunday), the clouds are moving east-to-west.
On proper onset, the clouds ,as we know, will rush in from the west or south west. Just a hint.
Meanwhile,let Vagaries remain simple and easy

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