Wednesday, August 11, 2010

Expected Low level circulation along Andhra coast... and its rain forecast...
A low level circulation is expected along Central Andhra coast for next 48 to 72 hrs.. this'll throw heavy showers for Andhra coast & inland

Monsoon easterlies being eased out from north-west

Westerly flows have started filling North-West India by easing out monsoon easterlies in the build-up to what is thought to be a ‘break monsoon' condition, or an intra-seasonal weakening trend in rainfall.
Break monsoon condition comes about in association with the northward shift of the monsoon trough from its normal position over Gangetic plains towards the foot of the Himalayas.

The monsoon westerlies in the lower troposphere extend right up to the rim of the Tibetan Plateau, a process that has been set already in motion over the Northwest.
Two other features – eastward movement of the westerly trough with large amplitude extending into West Pakistan and North India, and a high-pressure region over Arabia protruding into Central and Peninsular India – are also indicated, though not conclusively so.
During a break monsoon, heavy to very heavy rain is to be expected along the Himalayan foothills and Northeast India, and to some extent over parts of East and South-East India as well.
But the rainfall is comparatively muted along the west coast, if not entirely shut out.

An India Meteorological Department (IMD) update said on Tuesday that the western end of monsoon trough is likely to shift northwards during the next two days.
It is expected that the eastern end would also follow suit in another three days' time for the trough to move entirely to the foothills.
A warning valid for the next two days said that isolated heavy rainfall would occur over Jammu and Kashmir, Himachal Pradesh and Uttarakhand in accordance with the proximity gains vis-à-vis the incoming monsoon trough.
The 24 hours ending on Tuesday afternoon saw fairly widespread rainfall being reported from the Western Himalayan region.
It was scattered over Madhya Pradesh, East Rajasthan, the West Coast and the coastal areas of Orissa and West Bengal.

Satellite pictures on Tuesday showed the presence of convective (rain-bearing) clouds over parts of the Western Himalayas, north-west, East and Northeast India, the Bay of Bengal, Andaman Sea and north-east Arabian Sea.

An IMD outlook for Tuesday indicated the possibility of a feeble low-pressure area materialising over north-west and adjoining West-central Bay of Bengal under the influence of a persisting upper air cyclonic circulation.
Forecast for the next three days said that fairly widespread rain or thundershowers would occur over the Western Himalayan region during the next 24 hours and increase in intensity thereafter.

Fairly widespread rain or thundershowers would occur over East Uttar Pradesh, Bihar, Konkan, Goa, Coastal Karnataka, Kerala, Sub-Himalayan West Bengal, Sikkim, the north-eastern States and the Andaman and Nicobar Islands.

Scattered rain or thundershowers has been forecast over Punjab, Haryana, Delhi, West Uttar Pradesh, Central and East India during next 24 hours before scaling up in intensity.
Extended forecast until Sunday said that widespread rainfall with isolated heavy to very heavy fall would occur over the Western Himalayan region and adjoining northern plains.
Fairly widespread rainfall has been forecast for Central and East India.
Leh Cloudburst: 48.26 mm rain in 60 seconds ?? ...
As westerly flows have started into north-west India, this is a break monsoon condition ...
Heavy showers now into N-E Rajasthan as well.. !
"The Leh calamity is the latest devastating effect of unstable climatic change," ... Vandana Shiva, the renowned environmental scientist
Ladakh paradise lost in a global warning...
India Ladakh flood casualties exceed 185 ...
4:30pm, Heavy showers all over Punjab & Haryana, N. Madhyapradesh, U.P, Chatisgarh, Orissa and N.Andhra..
Chennai - A localized thunder shower is possible for central and South chennai in another 1 hr OR the present cloud formation will clear out
Chennai - Touched a max of 36.9 C (2:13pm).. and now 3:11pm we have good sea breeze and Heavy rain cloud formation overhead.
RT @JoMadelineMoore: Worst floods in Pakistans history Monsoon rains began on July 27
RT @Video_News_Now: Persistent Rains Thwart Pakistan Relief Efforts pakistan floods disaster msf un monsoon
12pm, Showers along N-E Punjab, Himachal, Uttarakand, Central U.P, central Bengal, N. Andhra...

The IMD 925 wind map shows that the westerly flows have started into north-west India by replacing the easterlies in connection with a ‘break monsoon' condition, weakening trend in rainfall.

Break monsoon condition occurs when the monsoon trough shifts from its normal position over central India, northwards towards the foot of the Himalayas. During a break monsoon, heavy rain is to be expected along the Himalayan foothills and Northeast India, as the eastern end of the axis moves into that region. "

Under the influence of an upper air cyclonic circulation, a feeble low pressure area is likely to form over northwest and adjoining westcentral Bay of Bengal today".- IMD bulletin today. This is also seen in the 925 wind map.
As discussed in yesterday's blog, this low would travel along the axis, and merge into it. As it moves, region around Delhi and western U.P. plains can expect heavy rains around this weekend. An extended forecast for this week would be rainfall with heavy falls over the Western Himalayan region. Resultantly,with heavy rains in the catchments of some rivers, we may witness some rivers overflowing into the Bihar plains from Sunday.

Along with this break monsoon, the days have started getting warmer, rather hotter. Yesterday's highs, as seen in this map, shows a 40c (Hissar), a 39c, (Ganganagar), and several 36s and 37s in the north.
Several places in the south have also started seeing higher day temperatures, with pockets recording 37c. As discussed in the "vagaries" on 9th. I would estimate Bangalore to cross 31c.

These hot conditions with moisture conditions would facilitate building up of thunder cells and thunder showers in the interiors of Gujarat/Maharashtra/Karnataka. These would be restricted, initially, meaning on Wednesday/Thursday, to interior Gujarat, and then thundershowers would pop up in interior Maharshtra and Karnataka from Saturday.However,thunder cells would not be widespread, and would be in pockets.

Mumbai: With the sun shining, the days have started getting to 32c. Likely to continue with such weather. With a daily average rain of less than 10 mms, till Sunday, one may tend to think the monsoon is over. But a shower to two will be a reminder that the rainy season is not over. Chances of a thunder cell drifting over Mumbai on Sunday from the east. But will not attempt to confirm that !
Chennai - HOT now 12:59pm, 36.2 C
RT @RAntoshak: India: Monsoon Remains Active and Trading Remains Brisk
From 15-Aug, Kerala & Karnataka coast will be active again with monsoon showers.
In next 4 days, showers to pickup over E.central & N. central India.
Widespread showers will continue over Orissa, N-E Andhra, entire N. India ... for another 48 hrs...
RT @rajugana: @weatherofindia, Baroda, 9.15am, Partly cloudy with sunshine inbetween. Dense passing clouds from SW.