Tuesday, August 24, 2010

The low in the bay finally appeared today,24th. August, and, is off the North T.N./ A.P. coast. At 1000 mb, it is persisiting, and lingering in the region since the last 24 hrs.From tomorrow, 25th.it should strenghten and move towards the A.P. coast. I estimate the system to cross the coast by the 26th, and at 998 mb pressure.
The WD25, mentioned in the "vagaries" has entered India from the west, as expected, and aligned itself with the monsoon axis. Resultantly, the Northern regions continued to
recieve heavy rains from the 23rd. and today's satellite image shows excessive clouding in
the U.P. and Bihar regions.

Today,the WD having moved away, now may not impact the direction of the bay low.The bay system should now take the axis corridor. The axis has now joined into the low as its eastern end. On crossing land, moving across A.P. and into M.P, it should precipitate rains along its path, and thru Vidharbha, and Northern Maharashtra, on 26th/27th August.

By the 27th.,it should fizzle out. BUT, a pulse emerging from the system, at 700/850 hpa,
should move ahead, and culminate into a vortex, or maybe a low, off the North Maharashtra/Gujarat coast around the 28th. Simultaneously, the off shore trough off the west coast will "liven up". Most models are in agreement.
Consequently, a much heavier rainfall regime should commence along the west co
ast. The rainfall areas will be from Karnataka coast/ Konkan and South Gujarat coast.
Some models are showing a very deep vortex, within the trough, and linked to the projected low which may form off the Gujarat/North Maharashtra coast. If it materialises, North Maharashtra coast (North of Mumbai) and Gujarat coast could recieve extremely heavy rains, upto 300/350 mms, around 28th. Saturday/ 29th. Sunday. The affected region, as of estimates now, would be North of Mumbai.Its a bit early to forecast t
oday, and we shall monitor this on daily basis.

To summarise, I would estimate precipitation as per these 2 weekly accumalated weekly rainfall maps of the next 2 weeks from NCEP/GFS. Of all the various models and estimates, I feel, these m
aps summarises the system's most probable rainfall track.


Mumbai: On reading the above, I feel, Mumbai should start with rains again f
rom Friday/Saturday
Friday: Frequent showers. Cloudy and overcast. Rainfall upto 20 mms.
*Saturday: Rainy condtions, and by evening frequency of rains increasing. Squally weather, with about 50 mms of rain, more at night.
*Sunday: Overcast. Windy and rainy. Heavy showers, with flooding. Rainfall on Sunday could be upto 100 mms.
*Saturday and Sunday forecast are subject to revision. Depends on the exact location of the Arabian Sea low, and the vortex, to be formed. As mentioned above, will be monitored daily, as important for Mumbai weather.

Leh got 240mm in 24 hrs on the fateful day - GSI

On the night of 5th and 6th August 2010, between 00:00 hrs and 00:30 hrs, intensive rainfall followed by massive cloudburst in high altitude terrain of Leh (3505m), triggered numerous debris flows, mud flows (earth spreads) and sand flows. These widespread, composite flows in the over saturated slope forming materials caused 182 deaths including that of 3 foreign tourists, damaged 607 houses, breached all major communication networks to Leh town besides inflicting an unaccountable loss of livestock and agriculture fields. The disaster caused severe damage to the settlements in parts of Leh town, Sabu village, Choklamsar, Leh airport area, Nimu, Ney and Bazgo area around the town.

The Deputy Director General, Geological Survey of India, Northern Region, Lucknow nominated S/Sh. VK.Sharma, Sr. Geologist, Ajay Kumar and Pankaj Kumar Geologists to investigate the affected area. The GSI team visited the area from 11th August to 16th August, 2010. Trans Himalayan region, known for its cold and desert type climate owing to scanty rainfall and high sun radiations, had never witnessed such a disastrous scenario since the recorded historical times, notwithstanding the fact that cloudbursts occur frequently in the higher reaches of the mountains.

The Leh region represents a broad U shaped glacial valley of Indus river sandwiched between the lofty high ranges of Ladakh in the north and Zanskar in the south. Huge piedmont fans, river terraces, recent flood plains with prominent point bars, lateral bars and Aeolian deposits are the major geomorphic units of the terrain. Lacustrine deposits, indicating neotectonic activity, at places, have been observed near Sputik, Phyang and Nimu localities. Geologically, the affected region is occupied by Ladakh Granitoids and Quaternary sediments of glacial, fluvio-glacial, lacustrine, alluvial and Aeolian origins.

Widespread occurrence of varied, unconsolidated Quaternary drift deposits perched over gentle to fairly steep slopes are susceptible to mass movement under conditions of heavy saturation. Unprecedented rainfall of the order of 240 mm within 24 hours on account of cloud bursts in the Leh region during 4-6 August 2010 caused excessive mass movement of drift deposits and over spilling of the banks of the streams. Huge quantities of debris charged water moved in high energy regime destroying everything in its run out path.

In Leh area, the damage was confined in the catchments of Shaksaling nala, flowing from an elevation 3800 m to 3410 m. The debris flow mobilized and damaged the settlements, Bus Stand building, BSNL buildings, Hospital Complex, Radio Station, etc. in its 3 km run-out distance.The Sabu nala section, located about 11 km east of Leh, was affected the most by the cloudburst. The prolonged and heavy rainfall that reportedly lasted for 30 minutes raised the water level by about 10-15 feet and triggered the movement in slope debris. Water charged with debris, wooden logs and huge blocks of granite choked the course of the nala at bridge points near villages Zong, Myek and Ayu Sabu. The village settlements, forest and agricultural fields were damaged on account of over spilling of water mixed with debris and boulders, which flowed out with an appalling velocity, resulting death of 11 persons in Sabu village. When the debris blockades at bridge points breached due to further on-gush, the debris flow spread out in the downstream commands. This phase, lasting for about 30-45 minutes, was, in fact, the major cause of devastation to Choklamsar village, ITBP Camp, Leh-Manali route, New Choklamsar market, etc. It is reported that bodies of 48 people were recovered from the debris from these areas. A pile of debris upto 4 m high was observed at Leh–Manali road near New Choklamsar village. The debris further moved and spread along the road before falling into Indus river. Typical accumulation lobes of finer fraction of debris material were observed at tail end of the flow. The total run out distance of the debris flow from the epicenter of the cloudburst in the Sabu nala to the tip of the debris flow was of the order of 10 km. The maximum lateral spread of debris flow has been observed to be about 2 km. The morphological dimension of the debris flow and lateral spread belies the current figures of deaths and damages in the area. Stokma nala, flowing adjacent to Stokma village, was blocked by huge boulders and wooden logs resulting in diversion of the nala course towards the right bank in a geomorphic depression /dry nala. The Druk Padma Karpo Institute, generally referred to as “Ranchoo’s School”, located within the flow direction of mud/soil/silt has been affected. The surge of mudflow entered the classrooms of the School.

The airfield of the Leh, one of the highest airports in the world, is uniquely situated in a ‘U’ shaped wide valley. The granite hills around the airport area are covered by a pile of piedmont fans, lacustrine deposits and top layer of Aeolian sand. The field area is on the fluvio-glacial deposits. The cloudbursts affected the airfield when sand /Aeolian deposits and a section of terrace spread out over the air strip, thereby hampering the air traffic, and to an extent, the rescue operations.

The natural depressions on both sides of nala and low lying dry streams, where sprawl of settlements have grown, were in general, the worst affected sites of devastation; the higherelevation of slopes were the least affected locations. The mass movement in geologically fragile Quaternary sediments under unprecedented saturated conditions was largely responsible for the devastation. The selection of sites for rehabilitation in the area should, therefore, consider the local geomorphic setting, the nature of slope forming material and potential run-out zones of mass movements.

Tropical Storm Danielle

Tropical Storm Danielle formed as a tropical depression over the Atlantic Ocean on August 22, 2010. By the following day, Danielle had strengthened to a tropical Storm, and had the potential to become a hurricane by evening, the U.S. National Hurricane Center (NHC) reported.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color image of Tropical Storm Danielle at 9:15 a.m. AST (13:15 UTC) on August 23. Danielle boasts the apostrophe shape typical of tropical storms, although it lacks a distinct eye.
At 11:00 a.m. AST on August 23, 2010, the NHC reported that Danielle had maximum sustained winds of 65 miles (100 kilometers) per hour, and was expected to strengthen further over the next 48 hours. Danielle 1,025 miles (1,650 kilometers) west of Cape Verde.
RT @DTNIndia: Above normal rainfall in Rajasthan this monsoon: Many districts of Rajasthan, including the desert regio. http://bit.ly/diY3Cb
RT @gaeabreaking: Two-day Malhaar festival hails spirit of monsoon http://pi.vu/rpP
12:30pm, Due to the Low along Tamilnadu and Andhra... S-W coast along Karnataka & Kerala are getting sharp showers... http://ow.ly/i/3nSh
12:30pm, Heavy showers along Central coastal Tamilnadu and seen marching inland ... http://ow.ly/i/3nSh
Chennai - Mild drizzles continue now 1:17pm... showers to become heavy towards evening.
chennai - Drizzle started in Sholinganallur, siruseri, Kelambakkam on OMR! (10:58am)
Upper air circulation & TS - "MINDULLE" ... http://ow.ly/2tLOz
Chennai - Having a heavy cloudy & warm morning so far 9:17am... more thunder showers expected after 12pm.
Today, Heavy & widespread showers coming up along N. Tamilnadu coast and S. Andhra coast...and coastal Karnataka ... http://ow.ly/i/3nJB
8am, Heavy showers along Central Tamilnadu coast, N.Srilanka and more showers coming up for N. Tamilnadu & Chennai .. http://ow.ly/i/3nJw