Monday, September 28, 2009

Let's continue with where we left off regarding the formation of the low in the bay.
Instead of Sunday, the low has formed in the bay on Monday, not too much off the mark ! On Monday, it is off the North A.P. coast and with a core pressure of 1000 mb. The streamline map attached is of Monday evening, and shows the low clearly formed.

Meanwhile, yes, the northern limit of the monsoon will remain stuck, for the time being (again), at the N. Maharashtra border and eastwards below Orissa and covering state of W.Bengal.
By the way, IMD has now removed the monsoon from North India today! Refer my blog dated 15th. Sept. I maintain the withdrawal status at that.

Now, the low, at present is showing good clouding bands in the eastern segmant, and with the projected movement eastwards, the expected natural consequence will be rains in interior Maharashtra and N. Karnataka next few days. The eastwards movement of the low can be a good sign of late season rains for the regions of interior Maharshtra and Northern regions of Karnataka, on Tuesday (29th. and Wednessday, 30th.).

The A.P. coast will also get substantially good rains for a day on Tuesday, and some "spill over" rains to precipitate rains to W.Bengal, and Kolkatta areas, but only for a couple of days.
But not much or meaning full rains in T.N. this week.

By the 1st. of October, the system could possibly carry itself into the Arabian Sea via Goa. On this day, that is the 1st. as a result, Goa, and north coastal Karnataka should expect heavy rains for a couple of days.

Some rains will extend into south Konkan also on the first 2 days of next month.

Possibly, the system may regain strenght in the Arabian Sea. But that we shall record and discuss in the next blog to follow on the 1st. of October.
We will possibly have to look east then, as typhoon ketsana is promising to send another low in the bay around the first week !
Mumbai: As "promised", after a dry weekend, some rain should resume this week. Tuesday should see a shower or two, and the day will be partly cloudy. Wednessday will see a thundershower, maybe towards evening. Some increase in rain is possible on Wednessday evening. Days will be hot at 33c, and nights at 27c will be above the normal by a few notches.

Friday, September 25, 2009

The push over of the monsoon southwards since last week, has resulted in good precipitation in the southern peninsula, as we had discussed in the previous blogs. The monsoon has been active over interior Karnataka during the last 8 days.

The immiediate effect of this active phase, was in Bangalore. Heavy thundershowers have been lashing the city last few days. The diagram shows the rain days over B'lore , after 11 Sept, and, there are quite a few days with very heavy rains of more than 50 mms.
But this has not resulted in cooling down the city to the extent expected. The temperature diagram of B'lore shows a major portion of the rainy days as "above normal', in the red !
Now, for B'lore, I expect an odd thundershower to pop up , in ther evenings specially, till the middle of next week. But the amounts of rain will be less than the previous days, maybe less than 25 mms. After Wednessday, the intensity of the rains will lessen.

Rainfall along the west coast and interior south peninsular India will now slow down, and will give the region some break for a few days.
This lull would be broken with the formation of the `low' in the Bay, forecasted for 27th. September, from when rains are forecast for peninsular and Goa and Karnataka coast.
A late-September low-pressure is likely in the Bay of Bengal around Sunday, and the monsoon maintains its precipitation over the peninsula.

Meanwhile,the cyclonic circulation over the east-central Arabian Sea off the Karnataka coast has become less marked as of Thursday, and has resulted in the formation of a trough extending south from Konkan towards the Kerala coast.
So, our watch for the low off the Goa coast is "called off". ( True to this year's monsoon behaviour). For the west coast, including Konkan, I would now concentrate on the upcoming low in the Bay, and see its effect.

Mumbai: A dull period with very little rain this weekend. Hot at 33c for the weekend with the night low at 27c. Pretty hot and uncomfortable. Some precipitation may resume next week.

Post Script: Dr. Uma from B'lore complains and is tired of the rains. Wants the rains to stop now! You're right and justified in this Uma. B'lore has got more than its fair share of rain. As on 25th. the city has recieved 700 mms, 300 mms more than the normal !
But the "winter monsoons" are not too far off !

Tuesday, September 22, 2009

Todays 925 streamline shows the border of the "active " monsoon south of the 20N line. There is a high pressure just above the line, indicating the "anti monsoon" pattern.
Southwards, low , just inland off Goa is seen.
Now, this is what we will be watching in the next few days. Many models confirm vehemently of a "good" system, maybe becoming a cyclone off the Goa coast.

That's why I still hang on to the monsoon persisting south of 20N including Maharashtra regions. In fact, I have always mentioned an isolated thunderstorm in Maharashtra, till the actual withdrawal, . Mahableshwar had a thundershower yesterday ( 21st, 22mms), and Pune had 10 mms.

Mumbai had its evening thundershower ( which I have been waiting for since the last few days), on Monday. The skies started getting dark in the late afternoon, as the upper parts of the thunderhead ( anvils) started spreading from the east. Day was hot at 32c and night an unpleasant 27c. But the rain at Colaba and S'cruz was just 2.1 mm and 1.6 mm. Not much of a boosting to the seasonal total.

Mumbai, continues with the chance of a thundershower popping up in the evenings. But things will change either way, once the predicted system forms off Goa.

Jim, in his blog mentions if it too late in the season now for a cyclone in the Arabian Sea. Or, if it would be uncommon to have one now.
No Jim. I dont think so. IMD, on its site sys, I reproduce :"Cyclones do not form in Arabian sea during the months of January, February and March and are rare in April, July, August and September. They generally form in southeast Arabian Sea and adjoining central Arabian Sea in the months of May, October, November and December."

In fact, there have been a number of occasions when a deep depression or a cyclone has formed in the Arabian Sea in Oct/Nov or even in Dec.
2008 - oct - DD, 2004 - sept - severe cyclone, 2004 - cyclone Agni, 2001 - 24th.sept -severe cyclone, 2001 - cyclone, 1998 - cyclone crossed Guj. on 17 oct, 1998 - dec - severe cyclone. Just a few notings of Sept/Oct period from the last few years.

Meanwhile the heat in the post monsoon regions has now risen, and Bikaner and Jaisalmer in Rajasthan were 43c yestreday.

Sunday, September 20, 2009

Two maps show post monsoon heat, and humidity pushing into the central regions of India from the west. And the streamline map shows the anticyclone over the central regions.

But, i would now like to wait a few more days, till the 23rd. to be precise, before we can say the monsoon has withdrawn from Mumbai/Maharashtra. So, the reversing is stuck at 20N, for some days.

The reason is, COLA and 1 more international model have indicated the formation of a low in the Arabian Sea, off the Goa coast. This may bring some precipitation along Konkan and interior Maharashtra, more so in western regions next week. But again, better to wait till the formation, and study its development and behaviour. Shall keep the development posted on this blog.
The current moderate to continue in the south for the next 2/3 days. And, ECMRWF forecasts a low in the south Bay around the 27th./28th.

And, the press is at it again ! The ToI reported on 18th. Sept that Mumbai has recieved 3600 mms of rain this year ! Wow !! thats 144 inches !! The actual rain is 1718 mm (68 inches) at Colaba, and 1932 mm (77 inches) at S'Cruz.
Wish the newspaper would clarify its a sum total of 2 rain gauges. And as on the 19th. this stands at -9%, roughly the same for both, Colaba and S'cruz.

Thursday, September 17, 2009

Todays 925hpa streamline map is sufficient indication of the monsoon having shifted south, below 20N. Strong northerlies/north-westerlies are now pushing drier air southwards towards the peninsula regions.

With no significant rainfall for entire North-west India, Gujarat and now into Central India, the monsoon is now seen pushing down south, and almost out of maharashtra, by Sunday, at the latest.

Jet stream easterlies, an important monsoon parameter, and indicated in my blog ,are steadily being pushed southwards over the peninsula and at 20N today, and moving further south, as on today (ECMWF map).

IRI ( Columbia University), forecasts Karnataka, Kerala and Tamil Nadu getting good precipitations from 16th. September. The result of a line of discontiunity, as seen in the 925 map from IMD.
But rains in the east and north-east may persist for 2/3 days more, due to a Upper Air Circulation embedded in the north-south trough in the W.Bengal regions.
For Maharashtra, a few isolated thunderstorms will pop-up in a few the regions of the state, latest till Sunday.

Mumbai: Still hopefull of a "concluding Thunderstorm" before Saturday. But again, from Monday, be prepared for a hot "post monsoon" week.

El-Nino: Seems the El-Nino was just gearing up the "harass" the Indian Monsoon. The SOI is yet to show any clear El Niño trend. According to the Australian Weather Bureau, the Southern Oscillation Index, a major indicator of a drought-bringing El Nino weather pattern, has become positive, "indicating development of El Nino has slowed".
"The Bureau of Meteorology said the index rose to one for the 30 days to September 12 from last week's 30-day reading of minus two. The official monthly August SOI was minus five. "The SOI is neutral and does not show an El Niño trend.
"The bureau said the index was more positive than expected, but most indicators suggested an El Nino was developing across the Pacific Basin, although progress had slowed in recent weeks. A consistently negative index points to the development of an El Nino".

So now, maybe better monsoons for the south this winter !!

Tuesday, September 15, 2009

For the states of Rajasthan, Gujarat, Haryana and Punjab, and M.P. the monsoon is as good as gone. The states of Maharashtra and Goa will get thundershowers for a couple of days, before the monsoon withdraws.

For Mumbai, it is a thundershower or two that is "pending", before the city sees the end of the monsoon. I expect the rains to actually stop by Friday/Saturday. (Hot post monsoon days next week!)

The remnant cyclonic circulation over west Uttar Pradesh had shifted east and now has been interacting with the W.D. trough to produce some showers over the region, but this activity would shift further to the east and northeast India.

And the seasonal monsoon trough having almost dissolved now, with the core at 1004hpa, against the normal monsoon core of 994 hpa, and with the "broken " axis shifting southwards, the focus of rain activity has shifted to the southern peninsula. (IMD map).

Pre monsoon withdrawal thundershowers will precipitate heavy rains for the next 3/4 days in Karnataka, Kerala, and Nilgiri hills of T.N. Western half of Karnataka, in particular, will experiance these thundershowers.According to IMD, a cyclonic circulation is above north interior Karnataka and coastal Tamil Nadu. This will bring the region under persistant thunderstorms for a week (from today), as the south west monsoon beats a retreat.
Under these condtions,we can expect an "earlier than normal" arrival of the north-east monsoon.(maybe 1st. week of October).

Post monsoon heat has started creeping in from the west, across the border (map).In Rajasthan, day temperatures have managed to become appreciably above normal to touch 40c and above at many places in this region.

Meanwhile, winter is setting in the northern most district of India. The minimum was -6c at Darbuk in Ladhak today. Srinagar was at 10.9c. In H.P. the cold places are naturally in the higher reaches region. Keylong and Kalpa were at 6c today.The winter trend setting in at this time in Kashmir and H.P. is normal, and almost on schedule.

Saturday, September 12, 2009

As mentioned previously in blogs, on Thursday, the well-marked low over west Uttar Pradesh merged with the W.D. present over north India as well as a cyclonic circulation over Jammu and Kashmir.

The result ? Very heavy rains and snow in the upper reaches of H.P. Rains figures upto 300 mms were recorded and many a places in the Punjab, U.P.and Haryayna received between 50 – 150 mms. In my blog last week, I had predicted good rains in the north due to this interaction but these rains figures are beyond my expectations !!

Some of the extremely heavy, and unusual rain recorded on Friday morning were:

HARYANA: (14 cm and above) Assandh 29, Nuh 28, Ferozepore Jhirka and Mewat 27 each, Nagina and Tazewala 23 each, Pataudi and Gohana 21 each, Jind and Massani Barrage 20 each, Berikhas 19, Naraingarh, Sohna, Safidon, Bawal and Jagadhari 17 each, Indri and Rohtak 16 each
HIMACHAL PRADESH: (6 cm and above) Pachhad, Karsog and Kandaghat 13 each, Dharampur and Solan 12 each, Jubbal, Kotkhai, Renuka and Paonta 11 each, Shimla, Nahan, Rajgarh and Kasauli 10 each
EAST RAJASTHAN: (6 cm and above) Kotkasim 31, Tizara 20, Kishangarhwas 15, Ramgarh, Kumbher, Kaman and Deeg 11 each, Kathumer 10,

Consequently, the seasonal rain deficit has been reduced to 20 per cent as on Wednesday (September 9), and will be further reduced by Friday.

But, due to the conditions of monsoon withdrawal, the rains could not actually “penetrate” into the western regions of Rajasthan, or rather, the system did not move westwards into the “no monsoon” area.

Now, as the system is getting weak, I personally see, the further withdrawal of the monsoon from the Rajasthan/ Gujarat regions these next 2/3 days. Maybe Western M.P. later.

For Maharashtra region, convective rains, that is, evening thundershowers, will be frequent now, a sure sign of the reversing of the rains in the state.
Generally this phenomena is common and expected for around 10 days, before the actual withdrawal.

Good and heavy thundershowers will drench all the regions, the interiors specially, of the Southern peninsula (Karnatak/Goa/A.P.and interior T.N.)next 10 days. Sure to lessen, the deficit substantially.

Mumbai: From Sunday thru Thursday, be prepared for evening thundershowers roughly with an interval of a day or two in-between. Afternoon/evening will see the skies darkening, and some showers in the evening/night will be the sequence of events.

An overnight thundercell from the ghats can , on some occasions, drift over Mumbai, especially early morning and precipitate some rain.

Wednesday, September 09, 2009

The expected process of Monsoon Withdrawal has commenced from the North Gujarat and west Rajasthan regions. The parameters indicating this are the low humidity in the mentioned areas (see IMD map alongwith), and day temperatures have begun to rise appreciably in northwest Rajasthan due to post monsoon conditions. The mercury has touched 40 deg C at Jaisalmer and a few other places.
And the nights have started getting cooler in the extreme north (thats where it starts from).
Like, places in Ladhak have dipped to -3c ( Chushul) and Srinagar reached 8.8 c yesterday.

Also, the western end of the monsoon trough (axis), normally fixed across the border, almost near Arabia, has now shifted into India. The exrtreme western low is in Rajasthan, as the MSLP map from IMD indicates.

Its a matter of these conditions persisting for another couple of days, and the monsoon can be considered withdrawn from this region.
The next W.D. will result in this winter's first snowfall in the higher reaches of Kashmir and H.P.
For furhter progress of the monsoon shifting southwards, we will wait for the current low to fizzle out.

The deep depression has been degraded as a well-marked low-pressure area and moved from west into Madhya Pradesh.
Meanwhile, the Bay has a fresh upper air cyclonic circulation on Tuesday. But, as per my last blog, I do not see it gaining much.
The IMD update said that Monday’s offshore trough from Maharashtra to Kerala had weakened, reducing the intensity of the rains over the region.
Next 2 days, i see rain only along the path of the weakening low. Wednessday rains can be expected in M.P/ north Maharashtra (Nasik and Jalgaon regions and Aurangabad). And on Thursday lesser rains in eastern regions of Gujarat, and in south Rajasthan to some extent.

After Thursday, rainfall will decrease markedly in Gujarat, Maharashtra, Goa and Karnataka and most of the southern region, till the end of this week.
For Mumbai: A few showers in some parts on Wednessday evening. Rain decreasing from Thursday thru Saturday. As rainfall will be meagre, tendency to gat warmer after Thursday.

Monday, September 07, 2009

Our ‘low’ over the Bay underwent intensification twice to become a deep depression, and become a numbered tropical storm, 03B. Central India and north-west India were spared from an expected heavy rains, as 03B took and went along a north-northwest direction track, and is estimated to keep moving to the north-west from here, and likely to merge with the W.D. in 2 days.
As a result, it is expected to precipitate heavy rains in U.P. and later, after a day in Uttarakhand.

Coastal Karnataka, Konkan and Goa have recieved good rains in the weekend due to the presence of the offshore trough along the west coast being fed in by the bay system.

But the weakening of the trough is seen as a result of the 03B getting dissolved, andhence, from this week (Tuesday) itself), i see a gradual weakening of the rain along the west coast.

The week the withdrawal of monsoon from north Gujarat, adjoining Rajasthan is possible. The step by step withdrawal of monsoon from more parts of northwest India will be monitored on its commencement.

Maharashtra, inland, too will have very little rain this week, and evening thundershowers may pop up by end of the week.

The IMD had mentioned about the likely formation of a ‘low’ in the Bay, but the Bay SST has reduced , as seen in the image, and has I have doubts as to upto what strenght the new low will muster up . The sea temperature in central bay has fallen dropped to some extent.

For Mumbai: Showers on Monday will be reducing late afternoon,with rain amounting to 15-20 mm for the day. Sunny intervals late afternoon.
Rains tapering off and much less (less than 10 mm) on Tuesday/Wednessday. Not much rain to bear up with next 48 hrs.

Post Script:I got an amusing query last night as to whether Mumbai has crossed the 100" mark rain this year. I replied in the negative, and was later told that it was reported so in the ToI on Saturday 5th. On going thru the report on page 3 of the edition, I quote from the article- "This brought the city's total rainfall during the season to 3375.2 mm, almost 75% of the annual rainfall." What was intended was the total was calculated by adding the 2 totals of Colaba and S'cruz ! If more rain guages across the city were added, it could have been much more !!
It was a bit misleading and not explained properly in the press.

Friday, September 04, 2009

Todays satellite image shows the clouds along the west coast sliding northwards, and the projected vortex forming over Mumbai.The city got very heavy rain on Thursday, 194 mm at Colaba.All along the Maharashtra coast, heavy rains were experianced. Many places along the Karnatak/Goa/Maharashtra coast recieved rainfall ranging from 100-200 mms.
This may last for a couple of days more in Konkan/ Mumbai, with Saturday getting a few more heavy showers, and tapering off on Sunday.
For Mumbai: Saturday: Heavy passing showers around noon, and evening. Cloudy throughout, with a high near 30. Chance of precipitation is 100 percent with rain amounting to 70 mm.

Sunday: A chance of fewer showers,tapering off after noon. Partly cloudy later, with a stray shower, and a high near 31. Sundays rain would be lesser at around 20 mm.
For golfers, Saturday will wetter than Sunday. An umbrella will be ok on Sunday, if you dont mind the slush.

The anticipated low-pressure area has formed over the Bay of Bengal off the Orissa coast.
The system is likely to become more marked during next two days, before crossing the coast, according to predictions by international models and IMD. Hence, Sunday to Tuesday will see an increase in rainfall activity over eastern coastal regions.
As the system moves westwards, and inland,from Sunday onwards, it will precipitate along the west-north-west track from east India covering southern Bihar, Jharkhand, Chhattisgarh, Madhya Pradesh, and later, Rajasthan and adjoining Delhi, Punjab.

Yesterday, a western disturbance moved in over Punjab and Kashmir regions.( mentioned in the previous blog). Resultantly, a trough in the north-west has made formed. This westerly trough, a sign of increasing "winter like" formations, can precipitate rain over north and north-west India, much like the "normal" W.D.s do in winter. I mention this, as i see this as a first sign of winter systems" taking over' in the north.

Hence, combined with the `low' moving west-northwest from the Bay, this will bring heavy rains after the rains in the Rajasthan, Punjab and northwest regions,

After these rains, I see the monsoon withdrawing after the 13th. in north Gujarat and Rajasthan.

Tuesday, September 01, 2009

Mumbai, Konkan and south Gujarat have been spared of heavy rains normally expected of a westward-bound rain being attracted to a low pressure system in the region of Gujarat.
Now, the low has fizzled out and moved away westwards in the Arabian Sea.

IMD streamline shows a fresh southerly winds being pulled in by activity in the west Pacific. This has resulted in good cloud formation over coastal Karnataka from Monday.
A round of revived monsoon rains will cover the west coast, pulling the rain up towards Konkan/Goa by Thursday.

A vortex forming in the north Konkan area is possible.

Hence, I expect Mumbai to get good rain on Thursday and Friday. Begining late Wednessday night, on Thursday, Visarjan Day, I expect at least 70 mms of rain in Mumbai. Thursday Morning/afternoon will see most of the rains. It could well be a wettish day for festivities. The rain amount will lessen to 30 mm on Friday.

Later, these rains will push into the south Gujarat coast.

We can now safely look out in the west-central Bay of Bengal and the neighbourhood for signs of a low-pressure area around September 3 (Thursday).
An upper air cyclonic circulation is already present over this region. It is expected to descend to the lower levels and deepen to form the ‘low.’

Today, ECMWF and IMD streamline maps show a line of discontinuity across north peninsular and adjoining central India today. As a result, the northern end of the line, H.P. got a very good bout of rains/snow. The day temperatures remained wintry and Kufri resort had a high of 14c on Monday, with Dalhousie at 15c during the day.

Now, a ‘low’ could get embedded into this trough by end of this week.
Thus the entire northern regions of the country would be brought under precipitation. This could last till September 10.

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