Sunday, September 30, 2007

Now its a hasty retreat ! The monsoon is pushing its way down south to widhraw at a fast pace. The dry air from the northern areas of Pakistan and northern most parts of India are vigourously pushing south as seen in this IMD streamline. The result:
1. Clear skies in Pakistan, North-west India, and gaining ground southwards into Gujarat,M.P. and eastwards towards U.P. Clear skies are prevelent today into Maharashtra.(IMD sat)

2. Resultant fall, overnite, in night temperatures in the north. Sudden falls in night temperatures recorded were 02c and 03c in Kalat and Skardu, and 15 c in Islamabad ( all Pakistan), and 05c in Srinagar, and 17c in Amritsar. Delhi has had a small drop to 21c. (see the southward thrust in IMD map)

3. Day temperatures may tend to rise ,for around the next 15 days, due to the sudden clearing of the skies.

Meanwhile, as mentioned, when the southwest monsoon widhrawal line reaches the states of Tamil Nadu, south Karnataka and Kerala, we have to keep a watch on the reversal of winds, to observe the arrival of the North-east monsoon.This may be heralded with a low, which may form around the 9/10 th. in the bay off the T.N. coast , as a result of remants of Tropical Storm "Lekima" near Vietnam.

The total rainfall of the season for Mumbai (Colaba) for the last three comparitve years.

2005: 2216 mm
2006: 2377 mm
2007: 2436 mm (97")

and Santa Cruz,
2005: 3321 mm
2006: 3030 mm
2007: 2569 mm.

Friday, September 28, 2007

With the rain bearing systems withering away, the process of the monsoon widhrawal has started , after a 3 weeks lag, as the initial widhrawal from the extreme west of India should have started from the 1st. September.
However, the lag may be reduced, judging from the current outlook. The 1st. Oct normal widhrawal line covers the areas north of Maharashtra, and west M.P. and western half of U.P. However, this alignment of monsoon termination line could be reached by the 7/8th. Oct. this year.
With the two existing systems over east India and the west coast weakening, and becoming less marked, the widhrawal phase of the monsoon is set to resume, as mentioned earlier.

Even though an "upper Air Circulation" is predicted by several models in the bay around the 1st. Oct, it is not expected to gain too much, and may not offer much resistance to the forward thrust of the anti-cyclone dry air winds pushing from the west.( IMD map shows the westward thrust of dry air)

Hence, in the first week of October, Eastern India will be witnessing pockets of thundershowers in places, and many areas of the southern region too cannot miss out on the popping up of convective thunder showers, squeezed southwards. Progressive drying up of the north, northwest will reach the south Gujarat coast.

Wednesday, September 26, 2007

The two concurrent weather systems mentioned in the last blog have now weakened. An update by the IMD states the Arabian Sea system has weakened into a "conventional"low, and the East India depression too has been degraded to a well marked low.
However, some international agencies give the Arabian Sea low an outside chance of intensification, as it is still anchored in the warm waters of the Arabian Sea.
On the other hand the eastern low is very much on the land, and will only weaken and fizzle out.

Then what is left for the monsoon to restart its widhrawal ?1. The 200 hpa westerly jet streams have reappeared and are dipping southwards again. They had briefly appeared about 10 days ago, but were overpowered by the monsoon systems. 2. The seasonal monsoon low over Pakistan has all but gone, with the pressure chart now reading 1010 mb. 3. An anticyclone clockwise winds are starting to blow over Pakistan/adjoining India.(map) 4. The humidity levels are falling in north west India, with dry anticyclone winds blowing. All these are signs of the monsoon widhrawal, and it is bound to start out from north west India within 2/3 days, and thence move slowly southwards. Dry northerly (clockwise) winds now establishing over Afghanistan/Pakistan, will play the key role in the southward push of the monsoon system.

Widhrawal heavy thunder showers will be the features over M.P, Maharashtra, south Gujarat and north Karnataka for the next one week.

Tamil Nadu and the southern tip of India, along with south Karnataka, will be watching the widhrawal of the south west monsoon. For concurring with the reversal of winds, the north east monsoon braces itself up right away.

Sunday, September 23, 2007

The events are developing, as mentioned, but without the sequence of dates as forecasted.
The low has become a depression and crossed Orissa on Saturday, pouring very heavy rain( 27 cms. at Athagarh in Orissa, and several places with rain between 14-24 cms in Orissa).
It is now moving North-West. Today, Sunday evening it lies centered over Orissa and adjoining Chattisgarh.( Heavy rain has been recoreded in Kolkata at 13 cms.). THe depression is likely to move North-West before interacting with the approaching W.D.

The Arabian Sea low has formed today. It, on the contrary has "sort of" interacted with the prevailing W.D. today and has formed a corridor of scattered rain north-south along western India/Pakistan border earliar than estimated by me.(NCEP colour image).

The Arabian Sea low is forecasted by the JTWC and the IMD to intensify. JTWC estimates a cyclone formation chance.
This is to be watched closely.

The result: A delay by a few more days in the widhrawal of the monsoon. The current depression will have to "rain out", and then the formation of the anticyclone can form over Rajasthan.
The last date for the monsoon to start widhrawal from Rajasthan, as of now, is 28th. September 197o. Will this year be a new record for the start of widhrawal ?

Rain will naturally be spread out over the states of M.P, Chattisgarh, east U.P. because of the depression. And over north India, specially Uttaranchal getting a heavy dose, due to the "interaction". West coast can get rain along with the Gujarat coast, if the Arabian Sea low intensifies.

Saturday, September 22, 2007

Carrying on from yesterday, the low in the bay has become a depression, and the low ,as mentioned, off the west coast, can be seen very well in this beautiful image from Dundee satellite.

Friday, September 21, 2007

The current week witnessed heavy rain along the northern peninsula belt and Gujarat. Alibag topped the list with an unusual 330 mms in a day, and many stations in Gujarat and northern Maharashtra with rainfall from 3- 10 cms.

The new low now off the east coast of India, is poised to become well marked into a depression by Saturday.
The depression is slated to travel inland across the Northern peninsula areas of A.P.,Maharashtra, M.P and towards Gujarat.

It is likely to merge with a low over North Konkan formed by the trough,seen well in the ECMRWF chart, by around Sunday/Monday, and the merged entity may move northwards towards Saurashtra.The system, if going by the estimate, may again interact with the "dipping" W.D. over northwest India and bordering Pakistan.
In effect, the monsoon trough will run along from Thar desert to the anticipated depression through central India.(current trough position,IMD)

In short, the effective result of this complicated meteorogical sytems interaction will be:

Heavy rains along the east coast of India from Friday, moving inland and good rains spreading through A.P. interior Mahrashtra and M.P. on Saturday(3-8 cms), with heavy rain in Mumbai and Konkan and the ghats on Sunday/Monday(4-9 cms). Rains will move towards Gujarat by Monday and will be fairly heavy in Saurashtra coast and inland(3-8 cms). By Tuesday/Wednessday(25th../26th.), rains will cover a corridor from Gujarat and South Sindh coast(pakistan), along Rajasthan/Pakistan border upto northern states of India, due to the interaction with the W.D.

This sequence of activity can be proved wrong, if the monsoon system, as unpredictable as ever, this year, decides to rearrange the jigsaw puzzle in some different pattern !It can happen, specially in the north, as the monsoon has "overstayed" its "booking dates there".

Wednesday, September 19, 2007

The south west monsoon has dug in with good rains over Maharashtra, A.P. and the south east parts of India yesterday and today. Yes, it has put its withdrawal schedule on waiting. This is due to yesterdays low pressure in the bay and the trough along the west coast forming a weak low along the Maharashtra coast. Even though the bay low has weakened into an "Upper Air Circulation", another low is forecasted to form around the 21st.

With the formation of this new low in the bay, the existing monsoon low over Rajasthan will slip a bit southwards, and the two lows will be the western and eastern ends of the monsoon trough, along the central region of India.
As a result, it can be mentioned, that the monsoon trough will slip southwards.
Along the west coast, the off shore trough will lead the wind flow to get organised, and form a new low over the North Arabian Sea by this week end.
The NCEP and ECMWF have forecasted for" wet conditions" returning to the west coast and central India till next week.

This will result in Mumbai and west Maharashtra geting heavy rain on this week end.Mumbai can get upto 75mms on Sat or Sun.

Thus, a wet spell can be expected from now for a week all over Maharashtra, A.P. and the north coastal Tamil Nadu.

This over active phase of the bay is a result of a constant feed from the South China Sea, due to a steady line of typhoons. From the monsoon point, these systems have a cascading impact on the "pulse" and Low formations in the Bay of Bengal.

In the North, an approaching W.D. is forecasted to dip south, and in all probabilities inter-act with the remants of the Arabian Sea low.This should happen around the start of the week begining 24th. Rain from this event can cover the Saurashtra region,Gujarat, north west India, Delhi, and west M.P. from next week.

for your views:

Sunday, September 16, 2007

The monsoon this year does not seem to be in a hurry to make an exit. By today, the monsoon should have normally widhrawn from Rajasthan, parts of Punjab and Kutch.
The 200 hpa jet stream winds, which had initially started its normal southward shift, has moved to almost 40 N today ! That is quite a push northwards considering the time of the year ! And, with day temperatures again at 45c in Saudi Arabia and 44c at Basra(Iraq), the monsoon low, at 1000 mb, has weakly reappeared (temporarily) in Sindh(Pakistan).

Good rainfall, pushing westwards from the Andhra coast and Orissa, will occur in Central India, interior Maharashtra, A.P. north Karnatak from Monday,17th.. Heavy rain will then be a feature, due to the low forming over the west coast, along the coast of Maharashtra and Karnatak and south Gujarat starting Tuesday,18th.The Konkan coast will get heavy rain on Wed/Thurs. I have my doubts if the Saurahtra region will get rain due to this system, as it will move west into the sea.
I had mentioned in my previous blog that the ridge like formation would spare the north-west of India from the rains. But since the ridge formation has been halted for the time being, and a weak low has formed, there may be a scattering of rains, by mid-week, due to the sytem mentioned, in parts of east Rajasthan and west U.P. and Delhi.

As for Mumbai, yes, the monsoon is far from over, as per the comment to my blog yesterday. Mon/Tue will see showers with about 10-15 mm/day, but Wed/Thu should see more heavy rain with around 50-60 mms.

As the widhrawal of the monsoon , from the north is behind the schedule date, Mumbai on its part too will see a delay in the rains departing. The normal date for the rains to bid goodbye for Mumbai is 29th. Sept. But there have been several years when it has widhrawn in the 1st. week of October. As per my personal records and information, the last date of widhrawal of the monsoon I have recorded in the last 30 years was on Oct 17th. 1985. 1983 was Oct.14th. and 2006 was 13th. Oct (how soon we forget).

For comments:

Friday, September 14, 2007

The widhdrawal phase of the monsoon seems to have halted at the extreme west of Rajasthan. True to its nature as throughout the season, this monsoon has become erratic and unnatural in its behaviour. The low humidity level, is now restricted to the extreme corner of India, where I think the monsoon is over. Also, the main factor of widhrawal, the 200 hpa winds, are now surprisingly moving back northwards.

Having moved north, it may allow the current new low in the bay to creep inwards, and cause some rain. As the low is too close to the coast, chances of its gaining strength is dim. Another low is predicted in the bay around the 20th. which is expected to gain strength, and by the 23rd. be near cyclonic stage. Its expected movement is to move inland through central India.

An interesting development forecast is a low forming over south Maharashtra around the 19th. and coming upto the konkan coast on the 20th. With this, it is expected that konkan should get heavy rain by then.

Mumbai, as a result, will get heavy rains from the 18th/19th.(around 20 mms/day), culminating into heavy rains by the 20th.(around 50-60 mms). Thus the temporary dry spell should end (with thundershowers), in a day or two.

The 2 lows from the bay, will bring in a fresh surge of rainfall into the northern parts of the Indian Peninsula, the west coast and parts of southern states too. However, the northwest region of India is expected to remain dry and out of reach of the new wave of rain.The seasonal "ridge like" setting over Pakistan and west Rajasthan ,which has started will prevent the systems from taking the normal north-west route, but push into central India.

At this stage, the monsoon overall is 3.5% above the normal average on all India basis. This IMD map shows the distribution of rain.

Sunday, September 09, 2007


The seasonal monsoon low over Pakistan and adjoining India was less marked today. The chart shows the low pressure at 1002 and moving over east into India, and as a "less marked", or a disintegrated low over Pakistan. I personally feel, with the winds having reversed over Pakistan, and the low getting less marked over the international border, the monsoon has started its widhrawal, and has retreated from Sindh and West Rajasthan. The 200 hpa jet stream is also moving southwards to support the reversal. However, the monsoon trough holds on into North India, , seen in the chart as a low, and is stationary over north India, hence delaying the monsoon widhrawal over the rest of Rajasthan and north west India by another 4/5 days. Accordingly, the the forecast by NOAA/NCEP show a total widhrawal from north west India by the 16th.

For the southern states, the IMD has forecasted the formation of an UAC by the 10th. This will result in an increase in rainfall over the region for the next 2 days.

The rest of India will have sporadic scattered thundershowers, Even though there is no organised system is in place, south west winds keep the moisture level high, to encourage convective thunderclouds into easy formations.

Mumbai will be hot and almost dry during the week, with a thundershower possible in the evening on Thurs/fri.

Friday, September 07, 2007

A Very Wet August Worldwide :

Moving away from the subcontinent weather, here is an interesting summary of the very wet and to an extent, destructive August we had globally this year. A datewise report from the corners of the world shows how the weather has been (and how much we were aware of):

For the month of August 2007:

Tropical Storm Chantal was responsible for heavy rain and extensive flooding in the Avalon Peninsula, Newfoundland. The worst flooding occurred in the southern areas of the Peninsula where many houses were flooded.

Severe thunderstorms struck Myanmar resulting in two deaths and many other injuries. The storms spawned a strong tornado that was responsible for two deaths and the destruction of 160 houses. Heavy rain triggered flash flooding which affected about 800 families and flooding many homes.

During the first week of August, areas across China suffered from heavy rain which triggered flash floods that killed 78 people and left 18 others missing

At least 14 people have been killed and 7000 forced to leave their homes by flash floods in central Nigeria. Flooding caused by days of heavy rain has also driven thousands of families from their homes in Lagos.
In Vietnam, flooding triggered by Tropical Storm 06W killed at least 70 people in central Vietnam and affected thousands more. According to reports, more than 48,000 homes and 65,700 hectares of agricultural land were submerged under water.

Three people were killed, 17 injured and 13 were reported missing in the Philippines yesterday after Tropical Storm Wutip caused floods and landslides. Tropical storm Pabuk was the first to hit the islands earlier in the week and was shortly followed by Wutip which churned across the country's Northern provinces early on Wednesday morning.
The rain which fell on parts of Switzerland this week was the heaviest in a century. In the Jura, 150mm fell in 72 hours - as much as normally falls during the entire month of August. Zurich, received its largest daily rainfall amount in 100 years.

Nearly 100 people have drowned and 335 injured in floods in Sudan over the last four weeks, caused when rivers burst their banks. Some 60 000 houses have been damaged or destroyed and 500,000 people affected. .
Typhoon Sepat developed as a depression in the western Pacific Ocean on the 12th, reaching typhoon intensity on the 14th.

Hurricane Dean developed in the Atlantic Ocean, west-southwest of Cape Verde, as a tropical depression on the 13th. Dean moved towards the Caribbean sea and by the 16th it reached hurricane intensity. On the 17th, Dean entered the Caribbean Sea through the St. Lucia Channel as a Category 2 hurricane.

According to a United Nations report, floods and landslides in the Democratic Peoples Republic of Korea have killed at least 83 people and 60 are missing

Tropical Storm Erin developed as a depression in the Gulf of Mexico on the 14th, reaching tropical storm intensity on the 15th. On the 16th, Erin made landfall near Lamar, Texas with maximum sustained winds of 35kn. Erin downgraded to a depression but dropped moderate to heavy precipitation in its path. By the 19th, Later that same day, Erin dissipated over northeastern Oklahoma. About 250mm of rain fell across Houston and San Antonio, Texas, as well as in parts of central Oklahoma, as a result of Erin.In Wisconsin up to 300mm of rain fell in some parts triggering mudslides.

Parts of Australia have been lashed by severe storms that have disrupted areas such as Sydney; parts of Sydney's north shore received more than 120mm of rain.

In the United States, thunderstorms brought heavy rain across parts of the Midwest prompting widespread flooding which forced hundreds of people to evacuate their homes

At least eight people have died after a heavy storm swept across parts of Poland; winds gusted at almost 120km/h through the Mazury lake district

Transport in Finland has been disrupted after a thunderstorm damaged the rail network; safety devices on the Helsinki-Turku line were damaged by the storm, leading to train services being delayed.

More than 300mm of rain has been recorded in the north-eastern part of Queensland (Australia), forcing many residents to evacuate their homes.

Approximately 50,000 people have been displaced by the recent flooding in Uganda. Six districts had been lashed by unusually high levels of rainfall for the last month before the flooding hit.

During August 22-27, heavy rainfall affected China's southwest region prompting flooding and triggering landslides that killed 17 people in the Sichuan province.

This year's wet summer in Canada has led to a surge in the number of poisonous plants growing in some parts of the country.

Really a wet month globally !

For your views;

Thursday, September 06, 2007

The normal date of the widhrawal of the monsoon from the extreme west of India and Sindh region of Pakistan is 1st.September. Clear skies and absence of clouds is seen from this area in the satellite image of this morning. The streamline map shows westerlies from Pakistan pushing into Rajasthan. But this is only the initial development, and cannot be "officially" put as the widhrawal, but only initial "moves", as the monsoon trough is still north at the foothills of the Himalayas. This trough should also move south, and create a reversal of the winds. The monsoon low is still prevailing in the Thar Desert as seen in this MSLP chart.

Hence, a weak W.D. is pushing the rains south towards the central peninsula.

Similarly there is no monsoon system developing in the bay, showing, most probably, no further signs of systamatic rains now. What can be expected in the next 3/4 days is sporadic "widhrawal" thundershowers along the west coast, North India, and central India, but heavy rain along the monsoon trough and the eastern end of the trough.

For Mumbai, a heavy shower or two, or a thunder shower in the evening, for the next 2/3 days. The rain may decrease after that during the day, with thundershowers in the evenings.

Jim(Accuweather) has given very interesting information about the deep freeze in the Antartic.
With his permission, I reproduce his write up:
" Plenty of nastiness of late, weatherwise, on the icebound white continent of Antarctica. At the Vostok station, the low temperature of -80.8 degrees C, or -113.4 degrees F, marked the nadir for the winter of 2007. It is the lowest temperature that I have seen observed anywhere (out of a small handful of Antarctic weather stations). Sunday, Amundsen-Scott station (the South Pole) observed -73.4 degrees C, or -100.1 degrees F--winter`s coldest by 0.1 degree C"

Very interesting and "chilling" facts, Jim.

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