Thursday, July 30, 2009

Rain-deficient Bihar and the North-East region received very heavy rainfall ( Cherrapunji gets 45 cms in 24hrs.) as the seasonal monsoon axis has aligned itself in position for enhanced rain in the foot hills of Himalayas. The actual rainfall map of the past 24hrs. shows very little or no rain in the rest of the sub-continent. Even the IMD daily rain map of India, attached here, shows the monsoon activity only along the foothills of the northern regions.
On the 30th,the axis of monsoon trough at mean sea level passes through along the foothills of Himalaya upto Raxaul and then Jamui, Asansol, Kolkata and thence southeastwards to eastcentral Bay of Bengal, a perfect position for the above pattern, and a "break monsoon " condition for the rest of the regions of the sub-continent.

The NCMRWF has projected its outlook for the ‘low’ by the 3rd. of August, with prospects of intensification.
However, international models do not indicate any major increase in rainfall over central India, that could signal a revival of the monsoon, even after the low forms,and crosses the coast.

Forecasting ahead, i would say, "status Quo" conditions, till atleast the 3rd. Similar rainfall pattern in India, as shown in the coloured rain map,and maybe with current rains along the northern foothills, shifting eastwards day by day.

Weak monsoon conditions to continue till the 3rd. at least.

For interior Maharashtra and Gujarat, the rains will remain weak and marathwada and saurashtra region may remain dry for the next few days. For the south, we may see rains increasing a bit along the coast,and shifting slightly inland, after Sunday, as the trough along the west coast may extend towards Kerala. For interoir Karnataka, no major development next few days.

Mumbai, weekend will be less wet, with less than 10 mm /day. Till Monday, Mumbai will be mostly bright, with stray passing showers in parts of the city. At 31c, and humidity at 80%, it will feel hot, as real feel temperature may be around 35c.. Punctuated by long sunny intervals, will make it more uncomfortable.

Monday, July 27, 2009

On Monday, the axis of the monsoon axis passed through Amritsar, Chandigarh, Nanital, Gorakhpur, Asansol and Kolkata and thence southeastwards to eastcentral Bay of Bengal.

Now, the western end of the monsoon axis has shifted north of the normal, indicating a dull phase for the regions south of the axis. And the westerly winds are blowing straight into the plains of north India (IMD streamline map).

It is not a particularly strong monsoon in the central/southern and western regions, including the north-west,now. Nor is it weak along the axis, as is evident from the heavy rains along the Himalayan foothills, Bengal and the north-east, which have been in deficit and need the rains.
Last week’s forecasts had indicated the formation of a weak ‘low’ in the Bay by the 26th./27th. It is now awaited, and hopefully soon that too. A fresh spell of rains along the central and north-western regions is required soon, but, the path of the forecasted low cannot be projected yet.
What I am fearing is the arrival of a ridge in the 500 hpa region from the west. If it moves along the path of north-west India eastwards, then we may have to bear up with a dry spell. This can be thwarted only by a low from the bay, which can literally halt the advance of the "dry" ridge. And that is what we in the sub continent must hope for ! .

For the next 2 of days,for India,the precipitation scene might just remain the same as on Monday.
Mumbai will have a couple of heavy passing showers on Tuesday morning and afternoon. With more sunny intervals after lunch time. Rain will be about 15 mms. But the rains will on Wednessday, when i expect less than 10 mms . A bit hotter on Wed. 31 c again like on Saturday.

Saturday, July 25, 2009

Some pics taken with my non-professional camera from Walkeshwar, Chowpatty and Breach Candy on Friday.

And for the blog, we just might continue reading from the last blog..Para 1) and 2) from the 23rd..... after the 1 days remaining rain predicted in Gujarat, Veraval getting 370 mms and Porbunder 150 mms and in the traditionally dry region of Kutch, Abdasa gets 303 mms,Nakhatrana 145 mms and Bhuj 53 mms. Now, the system and the rains have moved away westwards into the Arabian Sea. Though not going to affect Indian coast now, like I mentioned, this low will fizzle out now, as the Arabian Sea waters are at present on the "cooler than normal" side.

And, as expected. the rear regions of the system, now including all of central/ western and eastern regions of India, are clear of any major or meaningfull rains.

For the weekend, barring the Orissa coastline, I see the country as a whole getting nominal monsoon showers, nothing exceptional. Average normal rain showers along the monsoon axis( seen in the Thai map), for the next 2 days.

So, this sytem too has avoided the all important Punjab/Haryana /Delhi/U.P. and H.P. regions !

Till when this situation now? Of-course till we see another low in the bay. Now, this is forecasted by some models around the 27th./28th. and by some around the 2nd. of August. Could be the earliar date, as this map from the Thai Met. Dept. shows a trough running down the Bay, which makes an "in situ" formation easy.

Mumbai, expect a weekend with a few passing showers. Sunny intervals will be warm, as I think the day temperature will be 31c. With the winds sobering down, nights could get stuffy. Overall rain in 2 days will be around 25 mms.

Thursday, July 23, 2009

The low is moving away west. Within a day it has moved away towards the international border.

Now, the regions behind the system, are going get some respite from rains, (as it is the path of the system has recieved extremely heavy rainfall), while West Gujarat will continue to get rains for 1 day more.

Meanwhile, the south will continue to remain almost rainfree.

This despatch is with reference to the so called "threat" to Mumbai of flooding.

Well, Mumbai on Friday will recieve lesser rain than Thursday. To make it simple, on Thursday Mumbai city and suburbs got 15 mms and 25 mms respectively. On Friday I expect it to rain around 20mms , with regular bright intervals. And with lesser wind force, the wave force on the sea fronts should be the same as Thursday, even with a 0.1 metre rise in sea level over Thursday's height.

With the high tide time around 2 p.m, the actual amount of rain between 12 noon and 4p.m., considered dangerous for flooding, would not be much.

Hence minimum chances of rain flooding in interior city areas.

Some pics clicked from my cell at Haji Ali Seafront on Thursday afternoon.

After crossing the North Orissa coast on Monday, the depression (94b) travelled almost due west this week, and crossing Orissa, M.P. and covering Mah./Gujarat, and south Rajasthan to a greater extent, now lies as a low over Gujarat. The regions of north-west/north India, which are in need of rains now, was skipped ,as the system went along the axis line ,which had shifted southwards during the week.

The rain depicting colour image of Thursday morning from NOAA , shows the heavy rainfall area in Gujarat, and as on Thursday morning.

Now, since this system seems to have merged with the Upper Air Circulation of yesterday, and strenghtened a bit to some extent, some heavy rains have been recorded in Gujarat and North Mah. Rainfall figures will be available after Thursday 8.30 a.m., but Dwarka, we know, has got 190 mms of rain till 6.30 on Thursday.

System is expected to move west, and could re emerge in the Arabian Sea.

Now, the swirl seen over North mah. coast, attracted to the low could gradually loose its strengh over this area. As the system moves west, the pull be shifted towards the south Gujarat coast by evening, where there could be heavy rain from today evening.

For Mumbai, much is in store, with a high tide of 5.01 metres expected at 12.48 p.m. today, and agian at 1.30 a.m. on Friday morning

Now, if heavy rains coincide with the unusual high tides, there could be floodings along the nullahs/ sea water drains. Heavy rains, in "lay" terms would mean a very heavy downpour, say lasting at least 15 minutes (which could pour at least 15 mms in that time). Not one, but if a few such showers happen to occur, say between 11.30 - 2.30 on Thursday, it could create flooding problems along the affected areas. But, it also depends, subsequently on how much time the authorities take to clear the floods and drains, as the reverse tide will take a couple of hours to clear the drains.

Only a combination of rains and high tide will have to be observed.

But, with the current weather situation, as mentioned above, it is possible that there will be some heavy showers in Mumbai till afternoon. Rain intensity should lessen after around 1.30 p.m or around that time.

Tuesday, July 21, 2009

The attached map of Tuesday,from COLA, shows a vortex at the 700 mb level. Now this, looking like an extended cloud formation to the depression, has resulted in heavy rain, more than the depression itself, in Rajasthan. Kota recieved 85 mms during the day on Tuesday.

Not actually forecasted, or maybe the development went unobserved, but an upper air vortex can sometimes appear in the north-west in the form of . W.D,s in this seson also. And normally, an inter-action between a W.D. and a monsoon system, such as this one, usually precipitates the rains in the north-western regions and across the international border.

Of course the depression has resulted in good rainfall in M.P. today (Bhopal 111 mms in 9 hrs), and in Chattisgarh. But, ironically, (maybe due to the other vortex, I am not sure), the coastal and interiors of Maharshtra have remaind practically rain free !

And as expected, clouds have started diminishing from the southern regions. 19th. July forecast for the south holds good.

Now, with the system weakening,already it is a well marked low, and moving north-west, the upper vortex will diminish, and "make way" for the system. With this, the whole of Maharashtra, and coastal areas, and Gujarat should still get rain from tonite for the next 24 hrs. The monsoon axis will remain in its normal position for now, unlike a "break monsoon" position,as suggested by some agencies.
But i feel the expected initial "punch" is missing, and only the precipitation from a weakening system is now possible. A very short lived and fast depleteing system this one, much like the previous one this season.
Mumbai still holds on to the possibility of a clouds/rains on tuesday night and Wednessday.Maybe around 40-50 mms.

But as the IMD satellite image shows, the rear of the system is clear, hence, looking ahead a bit, Mumbai need not worry of exceptionally heavy downpours on Friday/Saturday. But we shall observe the situation day by day.

For the Gulf region, remants from the system which crossed the Arabian Sea last week , resulted in some persistant isolated showers todaynin the U.A.E. But these arevexpected to clear with no organised cloud formation possible this week. Back to hot weather !

The Deep Depression in the Bay crossed the Orissa /W.Bengal coast on Monday evening, and ,as on late Monday night, was centred at Orissa. The system has weakened from a core pressure of 988 mb. to 992 mb, by late night.
The satellite image (IMD) shows the core region of rainfall around the depression areas.
As the sysytem is supported by strong east/southeasterly upper level winds, it is now expected to move along the monsoon axis line, that is west-northwest, covering the states of Chattisgarh, M.P., Maharashtra, and south Rajasthan.

But it will weaken along its path, as it travels on land.
Resultantly, heavy rains are expected along its path,for the next couple of days, right upto the time it reaches Gujarat, maybe in 2 days.

It may be difficult for the solar eclipse observers in central India, and Maharashtra, to get a view of the event as the sky will be overcast during the event.

Very heavy rains will commence in Vidharbh from Tuesday, and heavy rains in Marathwada later on in the day (Tuesday).
For Mumbai, the day will be overcast, and should expect heavy showers, commencing from around late morning on Tuesday. Showers later in the day will be heavy, and prolonged, and as the system moves towards the west ( as anticipated !), the showers may continue and heavy downpours may persist with regular intervals into the night. Rain upto 60 mms could be expected on Tuesday.

Sunday, July 19, 2009

A low pressure area developed over northwest Bay of Bengal and off the Orissa/W.Bengal coast on Saturday. That is a day ahead of expectation. On sunday, it persisted,and became well marked. It is likely to intensify into a depression during next 24 hours.

Now, since the axis of monsoon trough at mean sea level, as on Sunday, passes through Ganganagar, Meerut, Bareilly, Gorakhpur, Dhanbad and center of well marked low pressure area and thence southeastwards to eastcentral Bay of Bengal, normally the system should move along the line of the axis.

(a):That means, after crossing the coast, it would move north-west. If so, the regions of U.P., and later Delhi,punjab and Haryana can expect rain sometime after the 22nd. In this case, Orissa, W.Bengal get initial heavy rain, and east M.P./Vidharbh get medium rain on 21st./22nd. till the system moves away.
But as I mentioned, it will depend a lot on the actual movement of the system, after intensifying into a depression. Because, there are contrary forcasts on its course of direction by different weather models.

(b):ECMRWF expects the depression to cross on the 22nd. and move west-northwest. That is towards M.P. In this case the north is avoided, and M.P./Maharashtra and later Gujarat get the brunt of rains.

(c): GFS today forecasts is movement to be restricted to the W.Bengal/Bihar region, before dissipating. In this instance, only Orissa/W.Bengal and Jharkhand will get the maximum benefit of the rains.
I personally feel, that tomorrow, the monsoon line of axis will slide southwards, and by the time the system crosses the coast for its inland journey, it will follow the new line-axis position. The monsoon axis should roughly be along the Rajasthan/M.P./Orissa line by tomorrow evening. (i am not putting this 4th. option as (d), since it is my personal view).

Bit confusing, I know, but one must be clear of the options possible before forecasting behaviour of a developing weather system.

Anywhichway, Konkan will get rains from Monday evening, and interior Maharashtra from Monday morning. Only in case of option (a) and (c), it will be shortlived, maybe for a couple of days, and lesser intensity.

Kerala, getting very heavy rains since the last 2/3 days, may see some relief now, as the moisture will concentrate along the northern regions of the west coast. In fact, the entire southern peninsula ( Bangalore included) may witness lesser rainfall for the major part of next week.

Mumbai on Monday will see passing showers between late morning and noon. Later, early evening will see the rain frequency increasing. Late evening/night outings may need rain precautions. Major bit of the 40 mms rain (cumulative) expected will be on Monday evening/night.

But, 40 mms is normally no cause for worry or panic. A decade ago (with less population and contructions), Mumbai was normal and flood free even with rains even upto 150 mms/day !

Friday, July 17, 2009

The prevailing ‘low’, by now, I feel, has become insignificant. and died out over west Madhya Pradesh.
The upper air circulation over Gujarat was almost stationary,and will also fizzle out after moving westwards. Today, (Friday) it has precipitated good rains in Kutch.
These two systems have been, dumping some exceptionally heavy showers in Gujarat/Konkan, as mentioned yesterday. 60 cm in Mangrol; 50 cm in Veraval; and 44 cm each in Porbandar and Dahanu.
The off shore trough would continue to be a bit effective, for at least 3/4 days, and rains of moderate intensity will continue along the coast.
The forcast of a new low forming in the bay , is still valid, and could be expected around the 19th.( Sunday). And the ‘low’ is also being forecast to track west, along the same direction as the prevailing one, and confine showers to the same regions, east and central India. Of-course, west coast will also benefit.
But I would not jump to a conclusion of its tracking direction yet. We'll wait till its formed, and observe the monsoon axis direction on that day. In fact its direction is very important, as therain hungry north-west region could be a big reciever of precipitation from the system.
Not only the tracking direction, I would not bet on the formation day too, in fact I feel it could be a day early.
Weekend means some good rains, lessening though, in Kutch and south Rajasthan. Some showers in W.Bengal, due to the eastern end trough line curving, some rain in Maharashtra, and central India, but scanty rain in north-west India.
For Mumbai: The weekend will be interspersed by passing showers. Not very prolonged, but a few could be heavy. Since the showers may not be too prolonged, they may be punctuated in between by sunny intervals. Average rain /day may not exceed 20 mms /day. Should not be much of a hindrance.
Holidays to Lonavala and ghat regions could be wet at times with prolonged heavy rain showers. Around 50-70 mms of rain can be expected in the ghat areas.

Thursday, July 16, 2009

The map provided by IMD for the latest monsoon status, shows a "happy picture" now, compared to last week.
The monsoon was in active phase over central and western India, and central parts recieved 67% above normal rainfall during the last week. And, the "red" areas from the west and south have vanished, replaced by the "normal" blue regions.
Much of the west and south now portrays a better picture and is in an improved situation.
Overall deficit is reduced to -26%. An organised system appearing after a gap of 5 weeks helped improve the situation.

The well marked low pressure which formed over northwest Bay of Bengal during 12-14th July , moved westwards across Orissa thereafter, and now has weakened over M.P. As a result, now, rains will decrease substantially over M.P./Chattisgarh, the interiors of Maharashtra and Gujarat from Friday. Coastal regions will also get reduced rains, as the trough will not attract enough rain bearing clouds to produce persistant heavy rains. The next couple of days, till the 19th, will thus produce reduced rains.
But, all this, not before unloading exceptionally heavy rains in Gujarat on Wednessday/Thursday. Unbelievable rain figures from Gujarat such as Mangrol-61, Veraval-50, Porbandhar, Dahanu-44 each, Maliya-42, Sutarpada-32, Vanthali, Bhanvad-21 each, Umargaon-20, Keshod, Lalpur, Dhoraji-19 each (all in cms), show the extreme intensity of the cloudbursts.

Now, as per several models, a fresh low pressure area is likely to form over the northwest Bay of Bengal around 19th July. (maybe the "pulse" effect of the system seen in the extreme east of the streamline map.
On monitoring this development, we shall be able to guage the next course of rainfall activity.

For Mumbai: Reduced rainfall during Thursday night , maybe a couple of showers. For Friday, again some bright intervals , and showers restricted to localities, may not be widespread across the city. Rain may not exceed 20 mms. for the day. If you are caught in the rain on Friday, take shelter and wait , it will stop !

Steady light/medium rain throughout the pre dawn hours, indicated a "wettish" night for Mumbai.

Now, the system from the bay is almost broken, and seems to be moving west, and weakening along its path.

So, for Mumbai, it should be a typical July day initially. A few heavy downpours, but I think the rains can reduce a bit by forenoon. A little "brightening up" possible around mid-day, but again, some showers could be expected by evening, more in suburbs.
Can expect around 30 mms of rain today.

Wednesday, July 15, 2009

For Wednessday, Mumbai had frequent heavy spells, yes. But not 60 mms. Colaba and S,cruz recorded 11 mms.each. Why ? Well, the rains missed Mumbai "by a whisker", if it can be said. This rainfall map shows the actual rain during the 6 hr. period on Wednessday, from 9.00 a.m.

The rain area is just off Mumbai, in the sea. And, it seems Gujarat coast, and interior Mahatshtra got a good bout of rain instead. IMD reports 292 mms of rain in Veraval, south Gujarat during the day today. Some other interesting heavy rain figures for Wednessday morning for places around Mumbai in cms: Mahabaleshwar-41, Matheran-31, Karjat-30, Santacruz-27, Dharavi, Mahad-25 each, Poladpur, Panvel-23

Rains had totally surrounded Mumbai. And spared it for the day ?

And, the low in the bay has now slipped inland and is over Orissa now. strong westerlies are still prevelent.

On the movement of the low inland, Mumbai should also have got heavy rains, as one reader mentioned. But, good or bad, the rains just by passed the city today.

For the night, I still think, looking at the situation, Mumbai can recieve at least 35 mms , to catch up on my predicted total. :) Some heavy showers during the night can bring the required amount of rain.
For tomorrow, let us study the behaviour and weakness of the erratic low during the next 12 hrs.

Special for Mumbai :
Shall try my hand at forecasting and in a way helping citizens to cope with the rains, or rather with the weather. Not too good at it, so help me out if I go wrong.
For Wednessday: It seems the low, at 992 mb. in the bay, is quite concentrated enough to continue pulling moisture from the Arabian Sea, and bring rains to Mumbai, and almost all of Maharashtra on Wednessday. The map in the previous blog illustrates this.
I will try to estimate rains quantum, for that will give a clear picture of assumption and one can get a clearer picture.
Mumbai, city, should expect around 60 -70 mms of rain today ( between 8.30 a.m. and 8.30 p.m.). Suburbs can expect 10% more, that is around 80 mms.
Showers will be frequent, with some rather heavy spells during the day.
Water logging possible during afternoon.

Shall update at night.

Tuesday, July 14, 2009

The much awaited, much forecasted and much needed low in the bay has finally formed. That too a dya ahead of the predicted date.The first system to form in the bay after 'Aila", the cyclone.

Today, 14th. evening, the system was as a well marked low pressure area over coastal areas of Orissa and adjoining northwest Bay of Bengal.

Now, quite unexpectedly, I admit, strong winds from the Arabian Sea got pulled towards the system and brought moisture, and heavy rain to Mumbai, and to many a regions of interior Maharashtra. The attached streamline map shows the winds directed towards the low. Normally, these winds would start when a system, specially a depression, crosses the east coast and travels inland.

Mumbai had heavy rains on Monday (120 mm in Colaba and 150 mm at S'cruz).On Tuesday, in 9hrs ending 5.30, Colaba recieved 44 mm while S,cruz got 166 mms ! Several other stations in Maharashtra too recieved heavy rains on Monday. Dharavi recorded 350 mms, Bhira got 166 mms and Koyna recieved 220 mms. In Chattisgarh, Arang got 340 mms, Raipur had 275 mms.

Now, with the inward movement of the system all of Maharashtra, M.P. and then Gujarat can start recieveing rains. For, if the system moves north-west, the parched regions of north-west India can get the much required rainfall.

On Wednessday, I feel mumbai should get around 75 mms of rain with rain intensity increasing in the night.

Like mentioned previously, the Arabian Sea low prospects have diminished.

Saturday, July 11, 2009

Its getting into the act now ! El Nino seems to be developing faster than expected.

US scientists say that the El Nino warming trend of the Pacific Ocean waters has returned, bringing with it almost certain changes in weather patterns around the world.
The El Nino climatological effect - the periodic warming of central and eastern tropical Pacific waters - occurs on average every two to five years and typically lasts about 12 months.
The US National Oceanic and Atmospheric Administration said the current El Nino was likely to develop further during the next several months, with additional strengthening possible and is expected to last through early 2010.

For us, in the sub continent, it is a certain El-Nino when the SOI, ( a difference in the pressures at Tahiti and Darwin) is -10. The latest figure has reched to -5.

The reason I am stressing on this now, is because, since the last 30 days, I see no proper system coming/developing for the Indian Sub Continent ( in the Bay, specially), in spite of several reputed forecasting agencies prophecising the same.

Today, 11th July, and yesterday, Rajasthan and parts of Punjab saw some rain. But, this was due to the interaction of the mentioned Easterlies with the Upper Air Circulation, now over M.P./Rajasthan. What I mean is , to get real Monsoon rains, meaningfull rains, we need a full scale system like a depression, at least. Till then how can such a big rain deficit (of the north/central/west) be wiped out ?

As of now, I do see any such system coming "in-situ" in the Bay till the 15th. The attached 825 hPa map shows the "UAC" in the west, another weak "UAC" over Bengal in the east, and the axis of the monsoon "line " joining the two. Rains are today seen along this axis line. With the fizzling out of the western UAC, I see the axis line shifting nortwards again. And diminishing the rains over the northern/central regions.
And the Arabian Sea low, seems to be a difficult proposition now. And if at all, it will too away to have any effect on India.

Mumbaites, my 4/5 days rain estimate will be over by Sunday evening. Expect less rains for next 4 days ( maybe 15-20 mms /day). And for Maharashtra, the winds rushing towards the Eastern Low, brought some rains (see map) last 2 days. Maybe lessening of precipitation next few days.
Gujarat, a day more of some rain, till the western low fizzles out. Maybe scanty rains next few days.

A fresh review, in a couple of days, may pop up some sudden surprises, hopefully.

Friday, July 10, 2009

Actual: 151.0 mm, Normal: 234.7 mm and Departure: -36%.
This is the position of the monsoon deficiency as on 8th. July. Much is being talked about the poor rainfall, and the scanty conditions Surely is a cause for concern.

The map shows the all India position. Broadly speaking, the south is now normal, and the rest of the country, west, east, north and central still" below." The overall Negative has come down, from the last figure in my blog of last week, from -56% to -36%.

Now, continuing from the last blog, the sequence of events seems to be taking shape.
I reproduce a paragraph from my prevoius blog, just to continue from there-:" But for north Konkan, and Mumbai,the inflow of substantial moisture bearing rain clouds could start "rushing into" the coastal regions from Wednessday evening itself. Heavy rains could once again start in from Wednesday /Thursday , and could, as a result of the system moving westwards,continue for the next 4/5 days.." Holds true today also. The land based low has moved west from Jharkhand, and the rains in the mentioned regions have commenced. The IMD streamline map (of 10th.) shows the monsoon trough also sliding south. The trough is now the "line" joining the 3 lows from Sindh to south rajasthan to West Bengal. And aptly demonstrated by the easterlies above the trough.
Now as discussed, these easterlies must bring in the moisture to the northern belt. But, only after the 2nd. projected low forms in the bay around the 12th. Now, 2 lows are awaited. 1 in the bay, and 1 in the northern Arabian Sea. Both predicted to appear around the 12th. On this happening, the full course of the rain path mentioned my blog dated 7th. could materialise.
Only one important change has occured (not occured). The Arabian Sea low may not become into a deprssion and head towards Oman as mentioned and projected.

(I am sorry to make frequent referances to my blog of 7th. But, this write up is almost like a continuation).

So, let us hope, and pray, that these 2 weather systems do form, and bring the much required rains in central/northern/western regions of the country.

In the absence of rains in the initial week of July, the temperatures in Gujarat, Rajasthan, Punjab,Delhi and Sindh regions shot up to markedly above normal figures. Ahmadabad had an all time high for July, recording 42.8c on the 4th. The days were at 43-44c in Rajasthan, and the night temperature in Bikaner was 33c. Also, 49c at Sibbi, was the highest across the border yesteday.
Due to this heatwave, isolated pockets in Gujarat recieved extremely heavy convective rains in the week. Unofficial reports from Bharuch mention of 82 mms of rain in 55 minutes on the 2nd, with a wind speed of 120 Kmph ! Baroda got 110 mms in 1 hr. 30 mins with strong gusty winds.

Tuesday, July 07, 2009

A land-based low-pressure area has formed over Jharkhand and neighbourhood on Monday.

This is now forecasted by a few international models to precipitate monsoon rains, initially,over central India during the rest of the week.
Model forecasts also estimate that this land based ‘low’ will take a westward course to move into central India, giving the much required rains in Chhattisgarh, north coastal Andhra Pradesh, Vidarbha, Marathwada and madhya Maharashtra.

Consequently, northwest India could also get get some rains as the westerlies along the monsoon trough interact with the easterly flows associated with the land-based ‘low’.
During this week, the system would attract moisture-laden southwesterlies winds, with rain clouds, from the Arabian Sea and is likely to commence a rain spell over western Maharashtra, north Konkan including Mumbai and south Gujarat.
But for north Konkan, and Mumbai,the inflow of substantial moisture bearing rain clouds could start "rushing into" the coastal regions from Wednessday evening itself. Heavy rains could once again start in from Wednesday /Thursday , and could, as a result of the system moving westwards,continue for the next 4/5 days..

Now, this land-based system, will be be chased by a second low from the bay, off the Orissa coast by Monday (13th. July). If true, this can make sure of that the wet spell started by the first low, continues for a further 6-7 days, in central India, as this would bring in substantial moisture from the bay. This, low, is forecasted by the IMD, and the European Centre for Medium-Range Weather.
The movement, and direction of the bay low is not forecasted or indicated by the models.
The ECMRWF also forecasts the formation of a low in the Arabian Sea by the 11th. But, this is estimated to move westwards, and "hit" the Oman coast around the 14th. as a depression.

Now, this day to day, step by step, activity and precipitation, is on the estimated and forecasted basis. I have seen, things go awry several times in the last 1 month.

Like, we have been waiting for forecasted lows from the bay for the last 21 days now. And, one suddenly shows up, un-announced. on land !

Estimates have either been delayed, by a few days, or a week, many a times this year, and I do not want to stick to fix days and dates this time. Not pessimistic, but realistic !.

Saturday, July 04, 2009

Maharashtra Special:
Due to the expected formation of a "vortex" of low pressure over the North Konkan Coast by Saturday evening, heavy rains can be expected in Mumbai, and Konkan from Saturday thru Sunday and Monday. On Saturday, Mumbai could recieve about 75mm of rain, 120mm on Sunday/Monday. Some stations in Konkan can get upto 200 mms per day.
Mahableshwar can also see the commencement of "real" heavy rains from Sunday thru Thursday, at least.
The rain are likely to move eastwards towards interior Maharashtra from Monday. Yet another low pressure circulation is forecasted in the Vidharbha/Madhya Maharashtra region from Tuesday. Hence, very good rains are expected in Maharashtra from Monday/Tuesday.
Madhya Maharashtra regions may recieve 50-60mms of rain per day from Monday for a couple of days.( Mahableshwar may get upto 400 mms in these 2 days).

Friday, July 03, 2009

The June rain figures are out, and as expected, the country as a whole is in deficit of -46%. Quite a huge deficit, considering the fact that June is the main month of rain and gets around 25% of the season's amount.
The figures are:Actual: 92.6 mm, Normal: 171.2 mm and Departure: -46%.

The sub-divisionwise weekly and seasonal rainfall distribution is presented in enclosed map. This shows only 1 region in the mainland as +, that is Rayalseema, and + in Lakshdweep Islands. Huge areas are seen in deficit or scanty shades.
The June of the last 5 years has been much better off. The June percentages from 2004 to 2009 were:-2%, -20%, -21%, +20%, +21%, and -46% this year !!
In Maharashtra, specially the inland regions, the deficit is alarming. -60% in Marathwada, and -50% in rest of the regions including Konkan. Rains in Mumbai are at 50% of the normal,( S'cruz at 40% of normal), and Mahableshwar( a key area for the catchment of 5 rivers) has recieved only 20% of its normal. In fact, the total for June in Mahableshwar was only 166mm (normal is 800mms). This is the lowest ever June total for this hill station, the previous being 194 mm way back in 1891 !
I have just recieved rainfall for June from Cmdr. Potey for Lonavala (hill station 100kms from Mumbai). June rain: 2009 =175mm( -85%). 2008= 1187mm. Normal= 1200mm.( my estimate). Thanks Cmdr.

In fact, in my previous blog, I had anticipated a low rainfall for Mumbai this week, Monday thru Thursday. I imagined the city would recieve 20-25mm per day. But, on these 4 days, Mumbai got an average of 10 mm only. Diagram shows the measly rain per day.

Now what? There is some positive and bright news. IMD, and some international forecasting models predict a definite Low in the bay, and the Arabian Sea around the 6th. of July. I feel, if this happens, and in all likelyhood it will, it will boost up rains in most of the deficit regions.
Strong wind flows from the Arabian Sea and the Bay of Bengal are expected to originate with the formation of the low-pressure areas around this date.
The Bay ‘low’ is forecasted to move west over land towards central India and most likely to merge with the system in the Arabian Sea, raining heavily all the way.
Entire central India, north peninsular India, Madhya Maharashtra, west coast,M.P. and Gujarat can recieve good rains along the path.

On Wednesday, the Australian Bureau said " more evidence of a developing El Nino event has emerged, and that computer forecasts show there’s very little chance of the development stalling or reversing.
The Pacific Ocean sea surface is currently significantly warmer than the long-term average across most of the tropical Pacific."

But, I feel, it may not affect our monsoon, not till August end, at least. An interaction of westerlies and easterlies around the Bihar/East U.P. region is precipitating heavy thundershowers. But these are short lived, and not expected to cause much damage.Once the lows from the peninsula seas get "in line", the easterlies will slide south towards central India along with the monsoon trough.
An eastward-bound MJO wave is already impacting the monsoon. It has "livened up" the coastal trough, as seen in the sudden surge of heavy rainfall events over the west coast. Hence hopes of quick revival, that is around the 6th. is more likely now.

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