Sunday, September 02, 2012

Mumbai Page Just Updated..1.00pm

A point by point review of vagaries' August forecast showed a 65-70% accuracy in the overall sequences of meteorological events and happenings in the month.
City wise figures have varied a bit with the overall prediction (of all cities combined) overshooting by 24%.(See Current Page for break up).

Come September ! 
One of the most dicey and difficult months to predict as far as the SWM is concerned. We have the "uncertainty" of the withdrawal, and we could have a WD unwantingly interfering with the systems and interacting with the Easterlies in the North, or we could even have a stubbornly active axis refusing to move down.
But, lets see and analyse what could be the scene this year. This year we have seen the Monsoon "yo-yo" up and down, from a scary drought situation when all and sundry joined the bandwagon in blaming everyone from the met dept to the Govt. Then suddenly, August picked up with 2 lows and an UAC from the Bay, creating an active axis and an unusually active eastern off shore trough. 

Now, September sees 1) A Neutral ENSO scenario. 2) A Neutral IOD position. 3) Below normal SST in the Arabian Sea, with Somali coast reaching 19c. 4) Strong Equatorial SW winds. 5) 200 hpa jet streams now Westerlies at 30N. 5) Western end of axis weakening slightly. 6) Siberian Tibetan pressure at 1012 today.

Points no 1) and 2) are not going to interfere this month with the normal flow. Point no.3) for forming coastal clouding along the west coast and 4) will favour that. 5) are just about normally placed, ready to move south at the call, which the weak low in Sindh is ready to give.
But, a stream of pulses, read lows, coming in from the Bay will keep the axis "alive" and prevent it from sliding in the first 10 days at least. 
Sindh (Pakistan) regions have some hope of one more spell between 5th-10th of the month.

Hence, presuming the MJO gets into a weak phase around 10th, and does not allow any lows to form or the monsoon to activate, we can expect a withdrawal from the North Pakistan and Sindh region after the 10th. Maybe 10th-15th ? By the end of the month, the SWM would be out of all states north of Maharashtra and AP.

So, rainfall could be "maintained " in the first half of the month in the Central (SE Rajasthan, MP, Gujarat) and Northern Peninsula regions. The NW region and Northern plains can have thundershowers in the first half of the month. 
Second half, sees more thunderstorm activities, precipitating heavy downpours in almost all of Central and Peninsula India. Rainfall starts shifting Southwards.

The rainfall for the Month would be near average. End of the season all India deficit may end up with a manageable  -12%-15%

September Rainfall estimate for:
Mumbai: 425 mms (Avg).  Outer Townships around Mumbai on Mainland around 550 mms.
Pune: 150 mms
Surat: 175 mms
New Delhi: 175 mms (Avg)
Bangalore: 200 mms
Chennai: 140 mms (Avg).

Estimates and Figures are worked out on basis of withdrawal and systems calculations. These are my personal calculations and may not be used for any commercial use.

Latest Monsoon Analysis from GSB on Inter Active Page..Must see


Pradeep said...

Rajesh Sir,

Surat Target seems very seeing the GFS forecast.

It should be revised to 300 mm

But anyways your prediction is always ahead of these models.

Letsee if its Vageries or GFS

Abhijit Modak said...

@ Rajesh Sir. Nice explanation and good job of rain estimation. I also used GFS model which states heavy rain for North Konkan & South Gujarat region in first half of September so assumed 700mm for outer township of Mumbai. Now lets see what is store in actual ! And today Badlapur received spells of rain in interval from early morning till late afternoon period which was moonsoonish type from SW. And afternoon had long heavy spell. So Badlapur records 30mms rain from 8.30am till 5.30pm today.

GSB said...


02/9/2012 ----------- 637 MM (-12%)
26/8/2012 ----------- 588 MM (-13%)

minimum 700mm ------ 2.25 mm p/d
average 900mm ------ 9.39 mm p/d
maximum 1100mm ---- 16.54 mm p/d

CURRENT RAINFALL is 6.78 mm p/d

COASTAL KARNATAKA ------- 336.4 mm
KONKAN & GOA ------------ 327.7 mm
A & N iSLAND ------------ 200.3 mm
KERALA ------------------ 160.2 mm
LAKSHWADEEP ------------- 147.4 mm

PUNJAB ------------------- 17.6 mm
GANGETIC WB -------------- 15.7 mm
TN & PONDICHERRY --------- 11.5 mm
JHARKHAND ---------------- 7.6 mm
BIHAR -------------------- 7.1 mm

Total ABOVE AVG days this week - 3

Total ABOVE AVG days
this season -------------- 26 (28%)

Total BELOW AVG days
this season -------------- 68 (72%)


NOTE: The required daily rainfall for a 900mm total Monsoon has gone over 9 mm.

Data from IMD. Any errors pls
point this out to me

Rajesh said...

Abhijit: (and readers interested in forecasting):
Let me very very briefly explain my modalities and method of forecasting. For long term forecast i see the overall surrounding situations like jet streams tendency, ENSO, IOD, SOI (important), and temperature deviations in western India, MJO,SST and several more, and of course the typhoons in the Pacific.
In winter, it is totally different situation and we have to move to see the Caspian Sea situation.
Vagaries does not follow any model. Sure, i refers to all models, and respects the job done by their scientists.
But, at the end of the day, i have to make my own judgement and prepare a forecast. May or may not tally with any model.May or may not be accurate. i cannot, and do not depend on any model forecast for short term (3/4 days). Every model (read COLA) is "permitted" to change every 6 hrs. That i never do. My forecasts will normally hold good for 3 or 4 days whatever i give, Thats the real test. If changing every 6 hrs is done, then there is nothing difficult.
The international models go on the psycological mentality of the normal person. Change makes the person forget the previous forecast put up, even if it was yesterday, and total attention is towards the newly put up forecast. Meteorological change, i know, but such variations in forecast is misleading to the acute follower of weather. It makes one just "go with the tide". No accumen is used.
Just mark, how accurate is a 7 day forecast of any model? and how many times do they change it? Yes, they are "allowed" to change it 4 times a day !!Oh, thats easy !
If one knows his regional weather, you can forecast with a reasonable accuracy.(above 70% is fairly good).
Preparing even a short forecast consumes a lot of time (and effort). But, then, long time followers of vagaries will recall, i have always said, each word in a forecast carries a deep meaning.

Latest forecast for Monday, i had put up 2 cities for heavy rain. Now , they with adjoining Marathwada are getting heavy rains today. Nanded is reporting good rain with Parli Vaijnath. Also, Akshy reports rains from Nagpur also today.
Vagaries survives on trust and faith. Cannot afford to let down any reader whether it s any facts or figures.
Sorry for the long message.

Pradeep said...

hmmm Sir, what a reply....

What you said 100 times to have put it has comment.

sset said...

Rajesh - Forcast for Bangalore sept - 200mm, I doubt. June-Aug it rained only 250mm, today,yesterday Bangalore was hot with no clouds.

Anonymous said...

Rajeshbhai, It has been great revival in Central India from the initial bleak outlook. As I have been mentioning little break is required to undertake de-weeding etc. But looks like we are in for a wetter Ganapati.

It was nice to read Sep forecast. Would look forward to overall status of Sangli, satara (rain shadow) region since local media is highlighting very poor status of precipitation and dam levels.


Rajesh said...

Cmdr Potey: Southern Parts of Marathwada and adjoining Vid got good rains today (Sunday). Monday too i see fairly good rains there.
The reservoir levels of Sangli and Satara as on 1st September:
warna (sangli) 100% full 2043 mms rainfall..
Krishna Dhom (Satara) 75% full.
Urmodi (Stara) 89% full.
Tarali (Stara) 84% full.
Dhom Balkawdi 97% full.

GSB: If you want to be accurate, the Normal rainfall level on all India as per 50 years avg is 890 mms this year.

GSB said...

Rajesh sir you are absolutely right! But since I did the 110 year analysis, posted on your blog, it was giving an all India average of 898.7 mm (which I then rounded off to 900mm). As the monsoon has changed it's behaviour over these past 110 years especially in the last 50 years I am sure the average must also have changed.

I assure you that next year's analysis will be more perfect and after consulting you the analysis presented will be of an even higher standard.

Pradeep said...

Venkatesh you asked about Coimbatore rainfall...yes last week it rained pretty heavily there

Chinnakallar - 400 mm in last 7 days
Valparai 250 mm in last 7 days
Sholayar 200 mm in last 7 days

Rajan Alexander said...

65% accuracy is very good. No model predicted IOD will spike to +0.7 deg C. BoM, Australia predicted 0.4 deg C.

At the time (3rd week July) you made the prediction, all model prediction for MJO for August was very grim. By the time you predicted, the same models gave an extremely positive outlook for August!

What can independent forecasters do differently as they are dependent on models of climate centers?

Another reason to chear up. According to a press report, the IMD predicted only 47% of LPA for August

Abhijit Modak said...

Badlapur got two thundery & lightening spell. First at 11pm & second one at today early morning at 5am from NW side.

Abhijit Modak said...

Yesterday Badlapur had mix weather conditions.

From early morning spray showers from south noted in intervals then heavy prolonged spell in afternoon time from SW, then drizzles till early evening. From 6pm sky was getting clear with sun out till sunset. Then moon & stars were visible till 9pm.

Then in night at 10pm onwards huge lightening & Thundering sound started with medium spells from NW side, Then midnight continued with drizzles. Then at early morning today again huge lightening & Thundering sound started with heavy spell from NW.

Now at moment dense black with medium spell going on.

So overall Badlapur records 65mms rain in past 24hrs.(i.e from yesterday 8.30am to today 8.30am on 03-09-2012).

Abhijit Modak said...

Very Heavy rain Lashing Badlapur from early morning with lightening & thundering.

From 8.30am till 10am(i.e in 1 and half hour) 70mm rain recorded here.

Just now lightening grounded to earth with severe flash and thunder sound in daytime which is seen for first time in my life.

Otherwise lightening strike mostly occurs in afternoon or evening or late night or early morning period only as I have it only that period only !

Rajesh said...

abhijit: Thanks for the interesting report...really surprising to see a thunderstorm today morning there.I see a line of storms north of badlapur to south, all inland..confirming our views, but not coming over Mumbai city.
Rajan: thanks for the compliment..a rare compliment indeed !

Abhijit Modak said...

@ Rajesh Sir. Heavy Rain snaps posted on Vagaries FB page.

And if we considered from 00am to 10am today then 100mm recorded here.

Yes I also very surprised to see lightening striking at 9.30am !! Because I am very fond of weather from mine childhood but never seen an thunderstorm rain at 9.30am !!

But noticed an thunderstorm from post noon till early morning 7am period..

But today surprising to see that last night lightening & thunder activity started at 11pm continuing till now! So now crossed 100mm mark from 00am till now.

Abhijit Modak said...

And I observing from last night that back to back Thunderstorms are generating from NW direction of Badlapur.

Abhijit Modak said...

Some Rain data in mms of mainland township around Mumbai region ending 8.30am today(03-09-2012).

Badlapur(own measured) 65
Ambernath 52
Ulhasnagar 49
Kalyan 47
Karjat 40
Panvel 23
Thane 20

emkay said...

Rajesh, suggest you can put up few of the things put up in comments here today as a FAQ for the blog. Very informative comments including yours. Those comments enlighten viewers about the process of forecasting.

NT said...

Some thundering heard here at Andheri (W) around 10:30 AM though not as heavy as pointed out by Abhijit at Badlapur. Rain has been light though the sky is overcast and it's gone very dark here.

GSB said...

Very heavy rainfall accompanied by thunder here at Thane. Total for today from 00 am is 53mm.

NT said...

Even as I was typing the earlier comment, it's begun to pour here at Andheri

Anonymous said...

first thunder heard at borivali west just 2 mins ago. (i live in a very noisy area so might have missed the light ones) also there was extremely heavy rain just 10-15 mins ago. but now the rain is moderate but the sky is very dark. also the low cloud movement seems to be from west-northwest (290deg)

Shri said...

-Same here....heavy rains with thunder in Mira rd..north of mumbai

Abhijit Modak said...

It's unbelievable to see that water resource dept of Maharashtra showing Barvi dam rain just 3mm ending 8.30am today.

On other hand Badlapur measured 65mm & Murbad also 32mm in same period.

So whether rains really escaped Barvi Dam site or wrong measurement !

Anonymous said...

Rajeshbhai, I was mentioning local media coverage of scanty seasonal rainfall around Jat, Jeur which is refelected in Pradeep's driest places.

There is widespread migration of people towards cities and women , children and cattle are in camps. Heart wrenching stories of deprivation and hopless future. ....Potey

Anonymous said...

nowadays its very common to see very localized rain. many times travelling between borivali and adjacent suburbs i have noticed heavy rain shower where i start driving and absolutely dry roads when i reach my destination just 1.5 to 3 kms away!! this happens mostly when the winds are calm. you can also notice this by looking at rain soaked vehicles on dry roads!!

emkay said...

News report of Morbe dam levels being unsatisfactory !! Bit surprising considering Panvel area received satisfactory rains till now !!

NT said...

Looking at the Doppler radar image, the heaviest rain is from Vasai-Virar / Bandlapur region till about Bandra, the city as yet looks to be on the drier side and then one can see heavy rain around the Roha region (south of Mumbai).

At Andheri the rain has been heavy and consistent but devoid of any Thunder activity as yet, however it's got even more dark now. The 00Z GFS forecast calls for 100 mm of rain in and around Mumbai for today.

Abhijit Modak said...

Badlapur records 100mms rain in just 3hrs.(i.e from 8.30am till 11.30am today).

Anonymous said...

Pradeep.very good stats.has made the monsoon very interesting this year.never got such info before.thanks.chetan

Abhijit Modak said...

Last 2 hours saw medium intensity rain. So 20mm rain recorded in last 2hrs.

And 120mm rain recorded here in Badlapur from 8.30am till 1.30pm today.

GSB said...

Mulund(w) gets 100mm rainfall in tha past 12 hours of which 92mm are in the past 6 hours.

Pradeep said...

Final Rainfall from Derecho that lashed Chennai ending 8.30 am on 03.09.12

I can see large number of trees fallen in the City while traveling to office.

in mm

Avadi – 65
Madhavaram – 44
Redhills - 43
Puzhal – 40
Chennai (Nungambakkam) – 39
Marina Beach – 37
Cholavaram Lake - 35
Poondi Lake – 35
Korattur Anicut - 33
Ennore – 31
Tambaram - 30
Guindy – 29
Poonamalle – 28
Kolapakkam - 27
Taramani – 26
Tamaraipakkam - 25
Ellapuram – 25
Chennai AP (Meenambakkam) – 23
Sholinganallur – 22
Poondi Agro – 21
Chembarabakkam – 21
Sriperumbudur - 20
Ponneri - 20
Tiruvallur – 20
RK Pet – 20
Uthukottai (Entry Point for Krishna Water) - 16
Sholinghur – 16
Kadambathur – 10
Thiruvalangadu - 10
Tiruttani - 10

Pradeep said...

Thanks took one complete day for compiling the data...!

Anonymous said...

hi rajesh, was this pure and sudden convective rains just across mumbai region or the vortex off mumbai coast that was bringing so much of sudden rains to mumbai....the clouding and the rains seem to be coming from the east...

Anonymous said...

What caused these rains over Mumbai and surrounding regions? 100 mm in 4 hrs. is serious stuff

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