Tuesday, June 30, 2009

The last 8 days has suddenly made all the difference and changed the total weather scenario, in the Indian region. The Monsoon, has moved, or jumped, northwestward by covering the states of Mah, Gujarat, Chattisgarh, M.P .Bihar and U.P. Delhi and parts of Punjab within with the last week. Thus, the northern limit of the Monsoon has achieved near normal levels after having lagged well behind in time and place by almost 15-20 days.

But now, onset/advance needs to be converted into normal rainfall, and as Jim from Accuweather puts it " for the details of atmospheric behavior under the setting of Monsoon are critical."

The June rain totals in almost all regions are below normal, that too to a large extent in regions of Mah, Karnatak to name a few. Details of the quatum of rain and deficit will be put up on this blog in a few days after the release of the details.
Now, this is predominantly due to be the lack depressions, the last was Tropical Cyclone Aila in the bay, and one depression in the Arabian Sea, fizzling out in 1 day over Gujarat.
After moving into Delhi today, mainly due to the Upper Air Circulation over the U.P. region, the monsoon may slow down for a few days. This can be due to the upper Air Circulation fizzling out due to lack of sufficient support from the bay.

And no "low" is forecasted yet in the bay, not till the 5th. of July .at least.
Rains may yet be subdued again in the states of Mah. Gujarat, M.P. Karnataka and the central/northwest regions of India. May not be a "break monsoon", but surely the easterly winds needed to bring in the bay moisture into central India will be missing till the 5th./6th.
But W.Bengal and the north-east may continue to recieve moderate rains, at times heavy, as the northern bay will be springing up a low in the next 5/6 days, and the moisture inflow into the W.B. coast may continue.

Normally, depressions deliver widespread rains in the main heartland of India. this year, the late onset and the absence of rain-making systems from the bay, is the reason for the deficit.
For the next 5 days, there is no indication of is any depressions.

Friday, June 26, 2009

A well defined trough along the west coast, with the recent depression at its "head", has resulted in some fairly good rains in nirth Konkan, and Mumbai on Thursday night/Friday (25th/26th). Along this region, Dahanu recived 65mms and Harnai 61mms, with Mumbai (colaba) getting 58mms, all as on Friday morning.

But, as I have been mentioning, the inland regions of Mah./Karnatak and M.P. are still dry.
The IMD now, as of June 24/26, has moved the nothern limit of the monsoon up the west coast into Gujarat and into interior Mah..
In the Eastern region, it is still the same, more or less. Onset regions as of the 24th june was two or more weeks behind schedule over central region, and eastern India, with little or no advance during last four weeks.

Hence, the overall rain as on 24th. June, shows a massive deficit of 54% ! Only 2 areas ( and Kashmir), in the IMD map, show a surplus, and vast regions in the central and coastal regions show scanty to below normal rains. Situation, as of the 24th, is surely not comfortable for the agriculture, hydro and overall economic scene.

A slowing down of the Westerlies into the northern Subcontinent has taken place during the last 2 days ( IMD streamline map below shows this). This should be seen as favorable,for a surge in and advance of the SW Monsoon in the next 2/3 days.

What is lacking are the usual Bay depressions. Systems from the bay are always instrumental in widespread rain into the central/western and northern regions of India. Depressions usually follow (by about one week) a western Pacific storm. This, I had mentioned, and anticipated last week itself for the typhoon "Linfa", but, there was no evidence from the storm. The bay now has to be watched again early next week in aftermath of" Nangka", now near Philippines.
Hence, the inland peninsula regions, will continue to be almost dry till first week of July. Along the west coast, the existing trough is expected to slide down , and linger off the Karnatak/Kerala coast from Monday onwards. Meaning, the rains in Konkan will reduce, to some extent, after the week- end.
Mumbai can get about 80 to 100mms on Sat/Sun. Thereafter, from Monday, it should get around 25mms/day for the next few days.

Wednesday, June 24, 2009

The low pressure which established south of Gujarat, rather suddenly and unforecasted, became defined on Tuesday, and became a depression, moving northeastward into the Gujarat landmass. Some very heavy rains,between 100 to 150 mms were recorded in the southern coast of Gujarat. As of Monday night, it made landfall near Diu.
Wind shear had earliar stifled its east cloud band and whirl.

Satellite imagery shows a marked northward spread of clouds, directly a result of the depression weakening on moving on land. Anyway,it is beneficial that this weather system has pulled the Monsoon northward following almost 18-20 days of stagnancy.

And, the IMD has ,on 24th. June, advanced the monsoon into Mumbai.
Mumbai was just one day behind the all time "last date" of monsoon advance, 25th. June in 1959. The advanced area now covers south Gujarat, parts of Kutch and Madhya Mah. Inland Mah. still remains out of the monsoon reach. The monsoon progress map is available on the IMD site.
Moisture flowing from the northbound lsystem will, for about the next two days, bring precipitation, though scatterred, into Rajasthan. These are pre monsoon rains, and not rains brought by the a "Western Disturbance".

Still, I do not yet see any well formed system,such as a Bay depression moving across the heart of India to bring widespread heavy rain in the regions the monsoon is yet to cover
The Arabian Sea system may also "pull" away rain clouds from approaching the Konkan and Goa coast, at least for the next 2/3 days.
Meaning, Mumbai will get only "passing showers', and the real monsoon may not yet pick up till 27th. June in Mumbai.

And yes. The IMD updated forecast of the monsoon season , as a whole over India , shows a deficient monsoon. To the extent of 93%. But, I would wait and observe the development of the Ell-Nino, in the next 30 days. There is a 60% possibility of it gaining in the next month or so.

Monday, June 22, 2009

A low pressure area formed over east central Arabian sea on Sunday evening, and on Monday lies over east centralArabian sea.Subsequently, the cyclonic circulation over east central Arabian sea off Goa-Karnataka coasts has merged with the above system. The trough at sea level from Karantaka coast to Lakshadweep area now extendsfrom the centre of the low pressure area to Lakshadweep area.
As a result, daily clouding with thundershowers are seen and experianced in the Saurashtra regions, and some moisture incursion in interior Maharshtra also occured.

But, as on Monday, the Monsoon has moved only upto Alibag, south of Mumbai, and is just off Mumbai now.It covers southern region of Mah. south of Pune. With the existing off shore trough and the low pressure in the Arabian Sea, the monsoon can move northwards within 24 hrs.

But, as discussed in my previous blogs, it may remain weak for a few days after advancing. Again, it all depends now on the low in the Arabian Sea. If it moves away from the Indian shores, the advanced monsoon will definitely get weak. But its moving towards the coast of Gujarat, will surely give an overall boost to the monsoon current. Effective heavy rains will be from Maharashtra to M.P.
Further north movement, is still hazy and uncertain timewise.
Heat wave conditions have re-appeared in west Rajasthan and adjoining Sindh. 46c at Ganganagar was the highest day temperature on Monday.

Friday, June 19, 2009

Continuation/Development from yesterday's blog.....
1. I would give importance to the Tropical Storm "Lnfa", in the South China Sea. The pulses from this storm are likely to travel westwards, and create a low in the Bay. By estimates, and observations of previous years, a low can appear in the Bay, from a system in the South China Sea, in this case as a result of "Linfa", after 5/6 days . That is around 22/23 June. This can help the monsoon intensify in the heartland of India.
2. The off shore trough, till yesterday holding on from Karnataka to Kerala, has now intensified a bit, and extends from Konkan to Kerala. Thus, the monsoon gaining strenght along west caost in 2 days seems likely. Thick convective clouds are seen off the Karnataka coast as a result.

Thursday, June 18, 2009

A low pressure appeared on the 17th. and fizzled out equally fast in the Bay. Within 24hrs, the much awaited low vanished as fast as it appeared.
But, today, the IMD has forecasted a further progress of the monsoon into north Konkan, and Mumbai by the 21/22 June.
This may be as a result of a surge, or a burst of thick clouding being forecasted to bring heavy rains, along the west coast of india. But, as per the COLA estimates, the heavy rainfall pattern is restricted to the region south of Ratnagiri (mostly to Kerala/Karnataka coast). The north Konkan- Mumbai region shows a very nominal rain of 5-10 mms in the week begining from 20th. June.
If the monsoon is advanced over the north Konkan by the 21st. it will most likely be as a weak current !
I feel, for Mumbai, it can still go beyond this date by a day . Anyway, the interiors of the states of Maharashtra ,M.P. and Gujarat will be looking out for the monsoon till the 1st. week of July.

By the way, the last date the monsoon has ever advanced over Mumbai, in its 130 years history is 25th. June. Never beyond that date.
And, the rainfall, monsoon figure, as on 17th. June shows a rain deficit of 45%, overall throughout the country.

Tuesday, June 16, 2009

Monsoon 2009: We had earliar termed the initial early start as a "false star." Now, I think we will have to call it a " ceased start" altogether !

No positive indications seem to be be buiding up as on today.

The ECMRWF does show a low in the bay around the 19th. Subsequently, as per them, it becomes a depression crosses the Andhra coast around the 24th. If this prediction holds on, then, we can witness a revival of the monsoon all along the "subdued" regions from the 19th.

The interiors of the central and southern Peninsula will get rains and the central regions, upto M.P. and south Gujarat can get rains between the 20th. and 25th. On the formation of this predicted low, the west coast, and north Konkan, can see a progress of the monsoon, which can then reach Mumbai by the 20th.

But, before counting our "chickens before they are hatched", I will wait till the low actually forms ( looking at the current behaviour of the monsoon).

And, the negative point ! A German forecast model, COLA, the NCMRWF (Noida) and at least 1 other International Model, show no signs of any low forming in the Bay around this date !!

The above models do not show any rains progressing, that is there is no monsoon progress as per them, till the 21st.from the current position.( Mumbai and Mah./Gujarat included).

In this case, then, the current monsoon regions will continue with weak rains.

Of- course, the Arabian Sea is devoid of any system forming till the last week of June.

For the SW Monsoon, very little advance is made since the last week in May. What had been a 1/2 week early advance has now become and retreated to 1/2 weeks behind schedule.
A question on everyone's mind, WHY? why have the rains halted their advance?

As mentioned in the last blog, the warming of the ses in the central Pacific, and the trend going towards an El-Nino phase could be one resaon.

Another factor is the still continuing W.Ds. As Jim puts it "`stubbornness` of the Westerlies to yield ground over the Pakistan and north India''. For the northern subcontinent region, due to the W.D.s, dry air from the west continues (even today), and sporadic rains, specially in Sindh and Rajasthan areas, have dipped the minimum temperatures to "undesirably" low levels. ( The deep blue tongue of extreme low in the map shows the sharp dip).

And the core pressure at the centre of the monsoon low has now risen to 1000 mb.

Now what ? Wait, and observe, day by day, the developments, and non developments, and as indicated, I will blog my observation on a day to day observation basis.

Sunday, June 14, 2009

We might just retain he first para. of my last blog, and reproduce it with the dates changed. The dates menioned, could just be pushed another 3 days ahead to 18th./19th ( for Mumbai included).

Can't help it !The conditions, or lack of it, are just the same.

The weak off shore trough off the Karnataka/Kerala coast will coninue to precipitate rains along that coast line. Sporadic local thundershowers will bring heavy downpours in the interior Karnataka/A.P./Orissa regions.(Due to the increasing heat).

But for the rest of the country, north of the current monsoon line, the wait continues.

No international weather forecasting model shows the rains, or monsoon, progressing northwards before the 19th. IMD announced the monsoon to be subdued till the 18th. And NCMRWF, Noida, shows the rains creeping into north Konkan (including Mumbai) on the 19th.
Interiors of Maharashtra and Gujarat can expect the monsoon to progress not before 21st., at least.

The main factor for the further delay is the fall in the pressure gradiant. The core pressure seen in the map is now at 1002 mb. Definitely it will be at least 3/4 days, if the reverse process starts now, before it recovers back to the 994mb level.

A heat wave in northern India only can "hasten " this in todays scenario.

As, the situation requires minute observation, we shall have another review in a couple of days.


Friday, June 12, 2009

And the wait continues.

No fresh sign of any developing low or systems either side of the Indian Peninsula in the next 4 days, meaning the subdued monsoon conditions are likely to continue , as on today, till the 15th./16th. at least. (Mumbai, wait at least till 15/16, Gujarat/inland Mah. till 20th.).

However, the ECMRWF forecasts the formation of a low, a monsoon forming low, in the bay around the 20th. of June.( Too lata, if true). The map from the ECMRWF site shows it. And the COLA map reveals it properly. Rain in forecasted week 12th.-19th, is along the southern coast, and in the subsequent week 20th. -28th, moving north into the central regions and the projected low forming along the east coast.

For the moment, minimal rainfall will be restricted to the coastal regions of Karnataka/Kerala for the next 2 days only. This is due to a weak off shore trough along this region.
Otherwise, very scattered localised thunderstorms will be prevailing in the interior Maharashtra/M.P. and northern peninsula regions next couple of days. This is mainly due to the local convection.

Thru my blogs, I am reviewing and observing the situation on a day to day basis. Today, with the monsoon stuck in a "half Monsoon " position, the synoptic situation can be very fragile, and could go in for a dramatic change, either way within 24/36 hrs. ( At very short notice !).

Another major, and unexpected, development is the forming of the El-Nino.
The waters of the central and eastern Pacific Ocean have started warming up. It seems to be heading towards the formation of El-Nino conditions within 2/3 months, according to some forecasts.
Now, I am far from being an expert on the El-Nino scene.. But I do believe that the sudden rise in sea-surface temperature anomaly occuring since the last March is--and will continue to cause the weather, and our monsoon, to behave differently than it normal pattern. Jim (Accuweather) feels this could be a reason for the "sputtering SW Monsoon?" Maybe. My thinking is that there may be a link too.

Tuesday, June 09, 2009

An exceptionally quiet day of weather on the Subcontinent.

What we were apprenhensive of, has actually happened !

We discussed in one of my blogs, a few days ago, about the monsoon actually "retracting" after the onset.
And , now , I feel, after seting in along the west coast upto Ratnagiri, it has almost become dormant in all of coastal Karnataka, Goa and south Konkan (the area mentioned as Monsoon Set).

Why ? Already discussed yesterday.

Whats there to look ahead now ? Without any "technical" elaborations, in brief, I would say, a continuation of the present conditions in the west coast, except Kerala, till at least the 14th.

Because, I see no system developing till the 14th. either side of the Indian Peninsula.

Quite clearly seen and justified in the COLA forecast for the next 15 days. The first 8 days are devoid of any meaningfull rains north of the Kerala coast, and inland into the interiors of central and western India. Also, forecasts of the MJO show the dry phase dominating for another week or so.

Mumbai, expect very light passing drizzles till the 14th. Infact, only a total accumalated rainfall of only 5 mms is estimated in Mumbai till the 14th. Normal for this period should be at least 55 mms. Gujarat and other regions north of Mumbai will have to wait even beyond the 15th.

Monday, June 08, 2009

After the fizzling out of the low from the bay, I obsereve something 'surprising", or rather something "unwarranted" at this stage of the advancing season !

The MSLP map and streamlines map from the IMD show a clear shifting of the yet unformed monsoon trough away from the normal east-west postion at 15N. We see a weak trough along the line south of the Himalayas, across Haryana thru the state of U.P.

The result of this is the upper air 200hpa jet streams, which should normally be east-west below the 20N line, are now in the direction mentioned below the 15N line. Pushed down for a few days by the "static" situation created.

Though this may,( and should) , change within 2 days, it is uncalled for at this stage. This development will "halt " the monsoon advance (again), and "subdue" it as per the IMD.

The advance of the monsoon along the west coast upwards from Ratnagiri will become tardy again for 2/3 days, thus lenghtening the wait for Mumbai.

Meanwhile, i would like to mention the unusually big "jerk" with which this "weak monsoon current" has moved into Goa and south Konkan. A weak current though, the monsoon movement northwards into Goa was with a whopping 43 cms of rain in Sanguem and 20 cms in Panaji, and 17 cms in Ratnagiri and 17 cms in Canacona (Goa). So, in a small stretch of about 75 kms along the west coast, massive amounts of heavy rain s have been recorded in 24hr periods.

The next day , the amounts of rain were almost negligible !

Saturday, June 06, 2009

Monsoon Watch-17

Something positive, to some extent, at last !

1. The pressure at the core of the seasonal monsoon low, which was at 996mb, as mentioned in MW-16, is now finally at the required normal 994mb. And the Arabian Sea is at 1008 mb. Enough differance to now make this sluggish monsoon edge up a bit. The IMD maps produced show a clear illustration of it all.

2. The central regions of India are also heating up to required temperatures again. Though not to any severe heat wave levels. Sindh had a high of 47c yesterday at Nawabshah. A sign of more heat coming into north-west/central India.

3. The south-west streamlines are very strong and appropriate below 15N, but still a bit weak above, that is north of Goa. Indicates a slow, but definite movement of the monsoon current north along the coast.

4. The much "dreaded" W.D. has moved away too far north to have any substantial effect on the proress of the monsoon.The 500hpa map shows this clearly.

5. After all this if we see nothing, Then all I can say is: "Its the Vagaries of The Weather" !!

Today, the feeble low in the north bay is half inland (into W.Bengal) and half over the sea (seen in the streamlines). The low, at most is an indication or "helping hand" for the monsoon to move a little northwards.

Why "little" northwards ? Because, I do not see the monsoon moving far beyond Mumbai, in the next 5 days from today.

No concrete signs of the monsoon getting a good push into Gujarat before 11th. are seen.

As mentioned before, the monsoon might still restrict itself to the coast of Maharashtra, (interior Karnataka can be covered by the monsoon due to the current low in the bay), and the interiors of Maharashtra may still have to wait till after the 12th. for a proper monsoon. This includes the Pune/Mahableshwar/Marathwada regions.

Mumbaiites, a couple of days more of sweltering heat !

Wednesday, June 03, 2009

Monsoon Watch-16
Monsoon Watch, Yes. I have been only watching the monsoon, and observeing its dormant state, and non advance !
What I feel about the state of the South West Monsoon as 3rd. of June is it seems to me that the SW monsoon commenced this year only to back off after an eventful start over Kerala. I have been mentioning a lull, but this is beyond my expectations.
Persistence influence of W.D.s, over the north of the Subcontinent is, perhaps, the reason behind the halting, or slow advance of the Monsoon for at least the last week. . Since the dissipation of Aila, my take is that rainfall within the regions where the monsoon has advanced, is been patchy and scattered.
Now, as per consistent forecasts, is shown to a northward spread of rain along the west coast as it should should be normally.
Except for the W.D.s, I fail to understand the reluctance of the rains to move north along the west coast ! The pressure gradient may not be strong enough, as the low is at 998mb., but the off shore trough along the west coast should bring rains along the west coast at least !
My forecast was for the movement of pre monsoon showers upto Mumbai by Wednessday, but I do not see any substantial cloud developments in the Arabian Sea as on today. The streamlines are ready, the Somali current is strong and the south west winds are "in form". Then why no pre monsoon movements? Your guess is as good as mine !
Only reason I see is the fall in day and night temperaures in the entire subcontinent northern and central regions since 31st. May, till date. See map and observe the "fall" in the subcontinent highs from 51c to 45c, as on today.
The forecast of Madden-Julian Oscillation -- MJO -- looking forward 40 days shows a setting to favor the suppression of convective rain for about the next fortnight.
Now what ? Coastal rains can resume "any day" but the interiors will stay devoid of real rains till the 12th. at least . Penetration of monsoon inland into Karnataka, Maharashtra, and upto Gujarat remains elusive till the 12th. of June, at least.
ECMRWF shows no upcoming low in the bay till the 12th. June.