Its been a day of mixed re-actions. weather-in-Mumbai wise.

Started of with the potential of good, heavy rains, with a big cloud mass forming overnite, and threatening the city with torrential rains. The satellite images put up, in the morning were indicative enough.

Then, during the day, it was yes and no.

Yes in South and Central Mumbai. Heavy, very heavy, rains lashed Central Mumbai right thru noon to evening hours. Flooding was the scene !

Colaba saw 55 mms till evening, while it was more in Central areas.

On the other hand, for some unanswerable reason, suburbs in the North had hardly any rains ! S'cruz recorded just 9 mms in the same period ! 9 mms, when conditions were very favourable for it to pour, and with dark overcast skies all day.

No. I do not understand the differentiating. In fact, Colaba has been favoured throughout this season :)

I see the rains easing out in South Mumbai,(will have to bifurcate North n South now), and surely lessening, and back to heavy shorter duration showers, with around 15 mms of rain on Saturday, and sunny intervals with 15-20 mms on Sunday.Monday forecast will be put up tomorrow night.

As long as the trough along the west coast holds on, the possibility of vortice formations are always there. The trough has now shrunk, and runs from Karnataka to South Gujarat coast.

Now, there is a distinct possibility of a low forming in the bay, by the 23rd.

Forming at 100 mb,may go deep to 998 mb, before crossing the A.P. coast around the 26th. This is as per the NGP forecast model. (Which I feel may hold good).

ECMWRF estimates no system at all for around this date!

There is a dim possibility, maybe 20% chance, for this new low to move Northwards instead, and cross straight into North Orissa coast.I say this,as the time of approaching the East coast, there is a strongish W.D. approaching, which may alter the track of the system.

Rain and track, will discuss as the low forms.

Rains have also eased off along the T.N. coast, with chances of a push again from the 24th.

By the way, Delhi recieved its heavy rains (forecasted in "vagaries"), with almost 200 mms in 2 days. Thats quite a lot, what with Parliament House roof leaking !

The axis has moved North, and estimates of very heavy rains in U.P. and Nepal holds good for the next 2/3 days.

7:30pm, Heavy thunder showers over Central Tamilnadu, Srilanka and S-W Bay is getting active... http://ow.ly/i/3jAc

AFGHANISTAN “DEVASTATED” BY MONSOON FLOODS ... http://ow.ly/2sj7q

RT @IntroducinMeerz: RT @farhanmasood: Monsoon rains caused worst flooding in Pakistan in 80 years. 20 million ppl have been affected

Nagapattinam (Tamilnadu) flooded..heavy rains from yesterday night.

Monsoon trough calls shots over north Pak, India

The seasonal monsoon trough lying along the Himalayan foothills and extending into Balochistan in Pakistan continues to dictate weather over the contiguous northwestern regions of the two countries.

A Pakistan Meteorological Department (PMD) update on Thursday said the ‘seasonal low' lay over Balochistan with a trough extending southeast. This formation could have implications for weather over Rajasthan across the international border.

CLOUDING PRESENT

India Meteorological Department's (IMD) satellite pictures showed clouding over Rajasthan and adjoining plains topped up by an upper air cyclonic circulation over west Uttar Pradesh.

The PMD also signalled to the presence of a shallow westerly wave over the extreme northern parts of Pakistan. This trough could get a move to the east to cross Northwest India over the next few days.

Monsoon currents of weak to moderate intensity emerging from the Bay of Bengal and fanning west-northwest into the plains of North India continued to penetrate the upper and central parts of Pakistan.

PAK RAINS

The PMD indicated the possibility of rain or thundershowers at scattered places (with isolated heavy falls) over Punjab, including Islamabad, and the province of Khyber Pukhtoonkhwa (erstwhile Northwest Frontier Province).

Meanwhile, the offshore trough along India's Southeast Coast deepened with a fresh upper air cyclonic circulation spinning up over West-central Bay of Bengal.

WET IN JAMMU

Satellite cloud imagery showed the presence of convective (rain-bearing) clouds over parts of the Western Himalayas, the Indo-Gangetic plains, Sub-Himalayan West Bengal, Sikkim, the North-East, Central and the rest of East India and North and South Bay of Bengal.

The IMD said in an update that the 24 hours ending Thursday morning saw widespread rainfall being reported from Himachal Pradesh, Uttarkhand, Haryana, East Uttar Pradesh, Bihar, East Madhya Pradesh, Sub-Himalayan West Bengal, Sikkim, Konkan and Goa.

A warning valid for the next two days said that heavy to very heavy rainfall is likely at a few places over the Jammu Division of Jammu and Kashmir, Himachal Pradesh and Uttarkhand.

EAST INDIA

Isolated heavy to very heavy rainfall would occur over Sub-Himalayan West Bengal, Sikkim, Punjab, Haryana, Chandigarh, Delhi, Uttar Pradesh, Bihar, East Rajasthan and the North-East during this period.

The forecast until Sunday spoke about the possibility of widespread rain or thundershowers over Himachal Pradesh, Uttarkhand, Sub-Himalayan West Bengal, Sikkim and the North-East. Fairly widespread rain or thundershowers would occur over Jammu and Kashmir, Punjab, Haryana, Chandigarh, Delhi, East Rajasthan, Uttar Pradesh, Bihar, Madhya Pradesh, Chhattisgarh, the West Coast, Lakshadweep and Andaman and Nicobar Islands.

WEST COAST

Fairly widespread rain or thundershowers would occur over Jharkhand and Gangetic West Bengal during on Friday before losing in intensity.

But scattered rain or thundershowers have been forecast for Interior Maharashtra and Interior Karnataka during this period and an increase thereafter.

Extended forecast until Tuesday indicated that widespread rainfall may break out over Sub-Himalayan West Bengal, Sikkim, Bihar, Uttar Pradesh, Haryana, East Rajasthan, Uttarkhand, Himachal Pradesh, the Northeastern States, Coastal Karnataka and Kerala.

IMD-GFS predicts less possibility of showers for Chennai, N. Tamilnadu and Andhra coast from Sunday, 22-Aug.

More Daily showers forecast for N. Tamilnadu, Chennai and Andhra coast till 27-Aug... as the LOW is expected over C.Bay and move in N-W.

A LOW pressure is expected over Central Bay on Sunday, 22-Aug... http://ow.ly/i/3jek

1pm, Showers over Interior & coastal Maharastra, N. Coastal Karnataka, central & N-E Andhra, M.P and Chatisgarh... http://ow.ly/i/3jed

Chennai - After early localized thunder showers... now 1:18pm its clear skies and temp is at 31. 7 C and rising... wind is from N-N-W

RT @labsji: Heavy showers at Nanganallur Chennai 10:20 PM 20 Aug 2010. cc: @weatherofindia

RT @labsji: Rain stopped completey at Nanganallur Chennai 10:30 AM 20 Aug 2010. It is sunny. too. cc: @weatherofindia

RT @rajugana: @weatherofindia,Baroda, 11.50am- cloudy sky with drizziles at times..

In a very sudden development, an UAC formed overnite over Eastern Maharashtra, and became well marked at 500 hpa. As nt, our reader pointed out correctly, it was sudden and unexpected.

During the night, I monitored the cloud mass, and observed it moving westwards. At 9.30, saw it approaching Mumbai at "super speed". A 4.30 IST rain map shows its proximity to Mumbai at that hour.
Cloud tops are at -50c, and could form 2 level thunder clouds.
A sudden burst of rain became inevitable for Mumbai.

All forecasts thrown away ! No model could forecast this rain spell !

As, we do not know when an unexpected guest will leave, unlike a planned guest who tells us his programme, we do not know the duration of this spell.

Big Cloud Mass nearing Mumbai. Monitoring the Cloud for Unexpected Change in Mumbai Weather.

Could lead to Heavy Rains.