Today, the LWD is seen from S Tamilnadu to N Karnataka and then to N-E... this is expected to persist for next 36hrs http://ow.ly/i/8P99h 

This LWD will pop more T showers over S,interior,W-ghats Tamilnadu, W-ghats Kerala, into S,E,N-E Karnataka, S,W,N,central Andhra in 36hrs.

S Tamilnadu HEAVY rainfall till 8:30am, 28-Feb..
Sankarankoil = 11cm
Mylaudy = 8cm
Aranmanaipudur = 7cm
Kalugumalai = 5cm.

RT @rajugana: Bangalore 3.15pm.., Sky getting cloudy.. patches of dark clouds from west..will it rain???? http://t.co/JEVk6HUKAB 
Bangalore - many zones of city got heavy T showers later in the evening !

Super W.D is now lying as a upper-level trough along 62E and dipping South upto 15N.. It'll drift East into W-coast India in next 24hrs.
By Monday morning, this upper-level W.D trough may fizzle out along W,N-W India... http://ow.ly/i/8P7UV 

The low-level circulation associated with present W.D is seen over N Arabian sea, S Pakistan, W Gujarat ... http://ow.ly/i/8P7ZY 
This low-level circulation will move N-E into India and reach to N-W India (N Rajasthan, Punjab) on Monday morning.. http://ow.ly/i/8P84i 

9:30pm, Satellite IR shows, rain and cloudy over most of N,W,central,E-central, central and S Peninsula ... http://ow.ly/i/8P8mK 
Reports of moderate/light rain over Mumbai, Badlapur and Pune today... and more ahead for these zones on Sunday !

Due to W.D, and before Monday morning...
Heavy, widespread rain for Madhyapradesh, Punjab, Haryana, S,S-W Kashmir, Himachal, N,E Rajasthan.
Moderate/heavy rain ahead for W,coast,central,N Maharastra, scattered over S,E Gujarat... http://ow.ly/i/8P8GJ 
Moderate/heavy rain ahead for Delhi on Sunday and scattered rain into W,central,E Uttarpradesh.
Showers will push to Bihar,N Bengal !

Today, a weak low-level circulation seen over S Tamilnadu and a Line of Wind Discontinuity seen from S Tamilnadu to central Maharastra. 
Today (Friday) as well the weak circulation over S Tamilnadu will prevail and LWD will also persist to central Maharastra.
On 28-feb, the LWD is expected to run from S Tamilnadu to central Karnataka and to S,S-W Madhyapradesh.. Rain ahead http://ow.ly/i/8NycJ 
As W.D trough moves East on Sunday, the LWD from S Tamilnadu will also drift East running thru N Tamilnadu to W,N-W Andhra to E Maharastra.

Nagercoil (S tip Tamilnadu) received moderate shower at around 1:15pm on 26-Feb.

Today... More scattered T showers ahead for Tamilnadu, W-ghats Kerala, Tamilnadu and into S, W Andhra.. http://ow.ly/i/8NyAZ 
Saturday again.. more T showers for Interior,W-ghats Tamilnadu into S,S-E,E Karnataka, S,S-W,W Andhra ... http://ow.ly/i/8NyKJ 
On Sunday... the scattered T showers again for interior, W-ghats Tamilnadu and into S,central,N-W,N Andhra.

@Valprajj >> Coorg - It'll be cloudy after 12pm and drizzles possible on Saturday, Sunday. No Heavy rain expected !

The upcoming W.D system is expected to bring HEAVY rain for many zones W,N,central,N-W and even South India from Saturday evening !!

Now, an upper-level W.D circulation is seen over Iran and another weak one over N pakistan.
By 28-Feb, the W.D upper trough is expected to deepen and move to 62E and dipping South upto 15N ... http://ow.ly/i/8NuCY 
On Sunday, this W.D trough is expected to drift into W,N-W India and continue to move East !

On 28-Feb, the upper-level W.D trough is expected to drop mid,low-level circulation over S Pakistan, N Arabian sea.. http://ow.ly/i/8NvaN 
28-Feb, morning, the low-level circulation is expected to be over N Arabian sea and in next 24hrs it's expected to move to central Rajasthan
1-Mar, low-level circulation will be over central Rajasthan and its trough will dip S-W upto N,N-central Arabian sea http://ow.ly/i/8Nvtk 

Due to this W.D upper-level trough and low-level circulation.. a strong moisture pull is expected thru Maharastra coast into Central,N India

Friday, before late-evening... scattered rain for E,central Uttarpradesh and into Bihar.
Upcoming W.D will push in Cloudy weather for W,N-W,N,N-central India from Saturday morning !
28-Feb, also, scattered rain expected for central, E Uttarpradesh.

From evening of 28-Feb...
Rain for W,N-W,S-W Gujarat.
Heavy for Punjab, Haryana, W Uttarpradesh, Madhyapradesh, W-coast,central Maharastra

From saturday evening/night into Sunday...
Heavy S-W monsoon style rain expected for Maharastra coast, #Mumbai ... http://ow.ly/i/8Nx0x 
Late-evening, 28-Feb to night of Sunday..
"Super Sunday Rain"
Mumbai, W,N-W,central,N Maharastra, Punkab, kashmir, haryana, Himachal, Delhi.
"Super Sunday Rain" also for ... central,N,E Madyapradesh, many zones of Uttarpradesh and Uttarakhand... http://ow.ly/i/8NxjC 

Back To Back Back Lightning Bolts. Western Disturbance 24 Feb 2015. Malout Punjab

Lightning Storm In Village Kabarwala Punjab. Pic By Sukhwinder Singh Amazing WD Thunder Storm Hit Punjab on 24 Feb 2015: http://youtu.be/-Du0FR30y80

24 Feb 2015 Thunder Storm Hit Malout Punjab

Amazing Thunder Storm WD Malout Punjab.

Amazing WD Thunder Storm Hit Punjab on 24 Feb 2015: http://youtu.be/-Du0FR30y80

Weather Instagram at February 25, 2015 at 10:53PM

Photo taken over SW Punjab on night of 24-Feb. Thunderstorm due to W.D system. #weather

from Instagram

Weather Instagram at February 25, 2015 at 07:23AM

Chennai - 6:50am, a cold February morning. 19.9 C with clear skies. #weather

from Instagram

Yuktix automatic weather station !

Yuktix provides automatic weather station that can send environment conditions from anywhere having cellphone network. Now keeping an eye on weather from anywhere is easy!

Yuktix AWS (Automatic Weather Station) comes in two versions

(1) Personal AWS : - Personal AWS comes with below specified sensor. With Personal AWS, weather enthusiastic can keep a track of changing weather conditions in their surroundings. They can see the data in real times pushed to Yuktix server at the frequency of 3 minutes in order to capture the smallest change. Same data stored in archive from where it can be downloaded for further research in future. 

Sensors

• Relative Humidity (+/-) 2% variation measured
• Temperature (+/-) 0.3 Celsius
• Pressure 300-1100 hPa (+/-) 0.12hPa at 25C (+/-)0.02mm
• Rain fall – accuracy of 0.02 mm

More sensor can be added on demand.

Yuktix cloud membership for 1 year is included watch and download data from your station.

(2) Professional AWS : - Yuktix Professional AWS comes with  below specified sensors along with sensors of personal AWS. Yuktix professional version of AWS can be used Agriculture research institutes, environmental research institutes and other government institutes to keep an eye of changing weather and do weather forecast as well as agriculture advisory by analyzing the  trend of weather in last few days or weeks. 

Yuktix also generate report at 8.00 am every days satisfying IMD guidelines which include Min, Max and Average for the previous day. More reports to be added soon. 

 

• Wind speed  ± 2 meter/hour, 0.1kmph,   max 160mph
  
• Wind direction ± 5% accuracy
  
• Leaf Wetness Dew / Dry Leaf/ Wet Leaf
  
• Soil Temperature -40C-60C, resolution 0.1C, 50C-110C with ±0.5C accuracy
  
• Soil Dielectric Permittivity Range is  1 (air) - 80 (water). For mineral soil/ potting soil/ rockwool/ perlite 
  

Pune will hover around 35c till the weekend..expect some clouding and drizzles on Sunday 1st March.

Western disturbance F-4 moving eastwards into the Indian Sub Continent on schedule..
Heavy Falls expected in Northern Pakistan and Pak Punjab on 24th and 25th. 
Islamabad can get as much as 35 mms rains in 2 days. 
Gujarat (Pak Punjab) can expect  30 mms in 2 days from 24th evening.

On 25th Kashmir can expect heavy rains and snow . Srinagar may measure upto 45 mms. on 24th Night and 25th , 
Indian Punjab, Utterakhand , Western UP  and Haryana may get hailstorms. HP hills get another round of snow and rains in the plains.
Light rains in parts of Delhi on 25th...but much more coming from M-1

Southern Tamil Nadu and Kerala likely to get showers on 25th.

26th rains decrease in North, but isolated heavy falls in Idukki district and Ghats of Kerala.Rains continue in Kerala till 28th.

Bangalore gets warmer to reach 33c by Wednesday, before clouds and light rains come on 28th...

The buzz continues into March...and the first week is really active in North and Central India...M-1 (Another WD) moves in the North on 1st March.

Projected 250 hpa level Jet streams as on 27th February

An extended trough into the Arabian Sea and West Coast of India can bring rains and Thunder showers to parts of Central India, Saurashtra and North and Interior Maharashtra ,North Konkan (Including Mumbai) on 1st March.

More activity and sensation from 4th March as M-2 moves in...!!

From www.vagaries.in

ogimet

OGIMET is a very good site which gives all global real time weather data.  Out Indian data is also included. Latest synoptic reports of  world wide countries, Latest METAR, upper air profiles of atmosphere of various regions of globe, cloud images, Meteograms etc.    
 Professional information about meteorological conditions in the world.
(1) 12Z Coimbatore synop:
 AAX 23124 43321 31996 00708 10310 21020 39665 40103 70500 333 10330 58007=

(2) 12 Z Nagapattinam synop:

AAXX 23124 43347 32997 10704 10292 20218 30101 40112 80001
      333 58001=

(3) 12 Z PAMBAN SYNOP  
AAXX 23124 43363 32997 20205 10302 20223 30100 40112 80001
      333 59001=
 
Latest METAR [timings in GMT] 
 

SA	23/02/2015 14:30->	METAR VOMM NIL=
SA	23/02/2015 14:10->	METAR VOMM 231410Z 07007KT 6000 FEW020 24/20 Q1013 NOSIG=
SA	23/02/2015 14:05->	METAR VOMM NIL=
SA	23/02/2015 13:40->	METAR VOMM 231340Z 08007KT 6000 FEW020 26/20 Q1012 NOSIG=
SA	23/02/2015 13:10->	METAR VOMM 231310Z 09007KT 6000 FEW020 27/20 Q1012 NOSIG=
SA	23/02/2015 13:05->	METAR VOMM NIL=
SA	23/02/2015 12:40->	METAR VOMM 231240Z 07007KT 6000 NSC 27/20 Q1012 NOSIG=
SA	23/02/2015 12:30->	METAR VOMM NIL=
SA	23/02/2015 12:10->	METAR VOMM 231210Z 08007KT 6000 NSC 28/19 Q1012 NOSIG=
SA	23/02/2015 12:05->	METAR VOMM NIL=

#Mumbai - SantaCruz - Today records a super #HOT day temperature of 38.3 C... http://ow.ly/i/8JrKM 

A weak easterlies is expected to affect S,S-E,central coast, adjoining interiors on Tuesday, 24-Feb... http://ow.ly/i/8JgfQ 

On 24.25-Feb, S,S-E Tamilnadu can get isolated T shower and many zones of coast,S,interior Tamilnadu can be cloudy, humid and warm.

#Chennai - expected to continue with the present temperature trend, 31 C and 21.5 C for next 3 days.
24,25-Feb.. can be cloudy till 2pm.

Now the W.D has moved away from North India... but it has given good scattered rain for Punjab, Kashmir and Himachal.
19-Feb, Bhuntar 7 cm

On 19-Feb..
Rain lashes Punjab, Haryana; Minimum temperature above normal levels...  http://ow.ly/Jqs25 
On 19-Feb, "Wheat crop hit by hailstorm in Punjab "... http://ow.ly/Jqs3F 
Rains worry potato growers; crops damaged at few places... http://ow.ly/Jqs5b 

Rainfall stats of 19-Feb,
Delhi-AP = 5.7mm
Chandigarh = 12.5mm
Jammu = 37.6mm
Amristar = 21.2mm
Ludhiana = 19.7mm

Rainfall on 20-Feb...
Bhuntar = 30.6mm
Shimla = 26mm
Amristar = 14.2mm

Next, W.D trough is expected to reach Pakistan, N,N-W India from Monday noon... http://ow.ly/i/8JfZL 
Kashmir, Punjab, W,N,N-W Rajasthan is expected to become cloudy from Sunday night due to next strong W.D system.
Heavy snow/rain to start for Kashmir, N Himachal from Monday noon/evening ... http://ow.ly/i/8Jg5R 

Weather Instagram at February 21, 2015 at 12:57PM

Hailstorm, night of 19-Feb. Photo from Fatehgarh pantoor near Moga, Punjab. #weather

from Instagram

Weather Instagram at February 19, 2015 at 07:13AM

Kabarwala, Punjab - 6:54am, very dense fog and 16 C, after 2 days of WD activity. #weather

from Instagram

During next 2 days, the minimum temps are also expected to be high over N-central Peninsula, Bengal and W India.. http://ow.ly/i/8GM62 

Day temps will be around 32 to 35 C over many zones of...
N,central, S Peninsula, S-E,S-W coast India, Gujarat and S,S-W Rajasthan.

#chennai - Expected to continue with present temperature trend, 32 C and 21 C.
Max temp will reach before 12:30pm and go down !

For N,central Tamilnadu, the day temps is expected to be around 33 to 35 C... http://ow.ly/i/8GMom 

A low-level(850hpa) circulation seen over E,S-E Uttarpradesh and sea-level circulation over W Bengal ... http://ow.ly/i/8GLr0 
Due to this circulation, T showers seen (6pm) over N-E Jharkhand, W Bengal.
In next 12hrs, Scattered T showers expected over N,N-E Uttarpradesh, Bihar, N,central,S Bengal.

In South India, moderate isolated T showers possible along N,central Kerala and S coast Karnataka in next 18hrs.

5:30pm, the last of present W.D system is dumping snow/rain over N,E Kashmir, Himachal and upper reaches Uttarakhand http://ow.ly/i/8GKae 

Next upper-level W.D trough is expected to reach Pakistan, N,N-W India on 23/24-Feb ... http://ow.ly/i/8GKOn 

Due to W.D, the day & night temps across N,N-central,N-W India remained above normal.
#Delhi Airport, day = 27 C(+4), night = 16 C (+6)

Posted Tuesday 17th Night:

F-3 precipitated rain and snow over the Northern States of India and Pakistan. Overnight, Amritsar got 20 mms, Srinagar 16 mms and Gujranwala measured 20 mms and Lahore got 16 mms. 

Next 3 days 18th/19th/20th, rains and snow will continue over the States of Kashmir (Srinagar 10 mms), HP and in many parts of Punjab (Amritsar 5-7 mms). and Haryana. Pakistan Punjab also to get showers ( Islamabad upto 5 mms, Gujrat around 5-7 mms) .

We can expect some light rains in Delhi on 20th. Meerut can expect light rains on 20th (upto 3 mms).
Mumbai will be clear , with warm days at 32c.
Kolkata will be cloudy on Wednesday. Thursday there can be light drizzles in some parts.

Due to a weakening of the upper jet streams (temporarily), the other WD, F-4, will be approaching Pakistan and Northern India  around the 23rd. Some respite from rains on 21st and 22nd in the North. F-4 expected to be strong with heavy rains, and much more can be expected in the Northern plains also. (Srinagar can get upto 75 mms on 23rd and 24th).

Another Fairly strong WD can be expected around the 1st of March (M-1).
From Vagaries.

1st Thunderstorm of 2015 in Kolkata

Listen to the Howling winds , Battering Rains and Flashing lightning ... 
Mass thunderstorm of 15th Feb 2015 .. Kolkata ..

In 24hrs, A low-level circulation is expected over Bihar and expected to persist along W Bengal for next 2 days... http://ow.ly/i/8DY5F 
Due to this, scattered T showers for S,central Bengal, N,N-E Odisha, and some into E Jharkhand on 15,16-Feb.. http://ow.ly/i/8DY8i 

Scattered afternoon T showers possible for S,central Kerala on Sunday, Monday.

A W.D is expected to effect Kashmir, some zones of Punjab and Himachal from Sunday night into Monday.. http://ow.ly/i/8DYbh 

RT @ShrivantR: #delhiweather pleasant start to the day, min at 14c. bright sunshine, low air pollution. expect max at 27c (11:42am)

#Chennai - Day temp has increased by 1 C.
Yesterday's high was 31.7C.

But the morning temp continue to be around 21 C.
#Chennai - 12:34pm, Another HOT and hazy day at 31 C.

Temp may not cross 32 C till February end !

#Hot Tamilnadu on 13-Feb...
Thirupathur = 35.4 C
Palayamkottai = 34.9 C
Salem = 34.4 C

Coimbatore = 33.6 C

Next 4 days, the day temp will be above normal ALL along W, S-W,S,S-central India and N,central Peninsular India... http://ow.ly/i/8DXYZ 

RT @ShrivantR: #delhiweather min today at 11c. max at 24c. clear and sunny, with low levels of air pollution @weatherofindia @SkymetWeather

Weather Instagram at February 12, 2015 at 06:37PM

5:07pm, heavy hail strom in Bhubaneswar. #weather

from Instagram

RT @ShrivantR: #delhiweather min today at 11c. light fog and heavy air pollution early in the morning.  @SkymetWeather (10:39am)

Today as well, the mid-level trough is seen along 69E and dipping South to 18N over N-E Arabian sea ... http://ow.ly/i/8Aj6C 
This mid-level trough is slowly replaced by an upper-level trough along 70E and dipping to 19N.. http://ow.ly/i/8Ajc2 
This upper-level (500hpa) trough is expected to drift East across central, N-central Peninsular India in next 3 days http://ow.ly/i/8Ajha 
The upper-level trough is expected to travel East upto East, N-E India by Friday, 13-Feb... http://ow.ly/i/8Ajmb 

3:30pm, due to upper-level trough, T showers seen over N Maharastra, S,S-W,central Madhyapradesh ... http://ow.ly/i/8Ajr7 

During next 24hrs...
Scattered T showers for S,S-W,central Madhyapradesh and into N,N-central,N-E Maharastra ... http://ow.ly/i/8AjyO 
By wednesday late-evening, showers expected to pop into N,central Chatisgarh, E madhyapradesh and even into W,S Odisha !

Today, easterlies moisture is seen affecting Coastal and South Tamilnadu ... http://ow.ly/i/8AivJ 

Scattered moderate showers possible for S,S-E Tamilnadu before midnight today.
Due to this easterlies... some showers may push into N,central coast of Tamilnadu on morning,mid-morning of 11-Feb http://ow.ly/i/8AiJT 
#Chennai - Surprise !! there's a 30% chance of moderate rain for city on morning,mid-morning of tomorrow, 11-Feb.

Dry and mild weather is expected to be back over N,central Tamilnadu from Thursday evening !

Weather Instagram at February 10, 2015 at 05:23PM

Chennai - 5:15pm, a mild 27C and dry evening after a cloudy midmorning. #weather

from Instagram

An upper air trough is forming over Central India which will destabilise the weather in North Maharashtra after  destabilising in Madhya Pradesh. Areas in Eastern MP are reporting thunderstorm on Monday.

Marathwada (Including Aurangabad,Jalna), Khandesh (Nashik,Dhule,Jalgaon),Western Vidarbha are likely to get  thunderstorms rains on Tuesday 10th Feb and Wednesday11th Feb. 
Heavy falls in Jalgaon region and Khanwa regions. Hail also likely .

Light rains also likely in South Gujarat Coast, (Navsari, and extending along coast till Surat).

Aurangabad can get light thunder showers on Tuesday and Wednesday evening.
Possibility of hails as well in around Aurangabad abd North Marathwada is not ruled out.

Weather will be normalising from Thursday,12th February 2015.

Next WD expected February over Northern Sub Continent...First Heat Wave around 17th February starting Odisha.
www.vagaries.in

RT @ShrivantR: #delhiweather cool morning with min at 12c. bright and sunny day to follow @weatherofindia (11:02am)

Most places of N,N-W,N-central India recorded a above normal day and night temp yesterday.
Today morning's low temp... Amristar = 4 C 

Weather Instagram at February 09, 2015 at 10:00AM

Chennai - 9:15am, a dry and mild morning. Photo of a super dusty road. #weather

from Instagram

Weather Instagram at February 08, 2015 at 09:57AM

Chennai - a mild morning to start.. Now, 9:55am, getting hot. #weather

from Instagram

Weather Instagram at February 08, 2015 at 09:52AM

Badlapur - 7:47am, First super dense fog of 2015. Nothing visible beyond 100 feet. #weather

from Instagram

From Vagaries

Now, an upper-level W.D trough is seen tilted, N-W from central Asia to N-W India ... http://ow.ly/i/8xOTX 
This W.D trough is expected to become a N-S trough in 24hrs and drift into N-W India on Sunday and weaken .. http://ow.ly/i/8xP1v 

The W.D trough has already induced a weak low-level circulation over S,S-central Rajasthan ... http://ow.ly/i/8xPeR 
This low-level circulation is expected to drift East into N Madhyapradesh and fizzle out on Sunday noon... http://ow.ly/i/8xPne 

W.D low-level circulation is expected to give scattered rain over E,S-E Rajasthan, N,N-central,central Madhyapradesh, S U.P on 7,8-Feb.
On Saturday, Sunday ... some showers will push into S,central Uttarpradesh and N-E Madhyapradesh... http://ow.ly/i/8xPKa 
Delhi on 7,8-Feb...
Expected to be cloudy at times, a light rain possible and max,min temps will be around normal.

From Saturday, noon till Sunday, evening... Snow/rain expected over Kashmir and N Himachal.

For Tamilnadu coast... an easterlies is expected to reach on Monday noon ... http://ow.ly/i/8xNLf 

This easterlies is embedded with a weak low-level circulation over 5th parallel near S-E Srilanka coast on 9-Feb.. http://ow.ly/i/8xO61 

For coastal,central,N Tamilnadu...
Saturday, Sunday is going to be cloudy and warm till 2pm.
Morning will be mild around 22 C.

#Chennai will have another 3 mild mornings with temp hovering around 22/23 C.
Warm and partly cloudy day expected till 2pm.

Weather Instagram at February 06, 2015 at 09:28AM

Chennai - 7:15am, a mild February morning. Can get warm on 7,8-Feb. #weather

from Instagram

Stormy conditions in south coastal India

Sir/Madam,

We had intimated you regarding the high chances of a storm at Alabama, USA,  on 26^th January IST  i.e. 25^th Jan, USA time. Our forecast was correct, which was made almost two weeks prior to 25^th Jan, much before any forecast by National Weather Service, USA. The report of NWS, USA, is attached.

Our next forecasts are as under:

a)      There is a high chance of stormy conditions in the coastal belts of Southern India likely to be on or around 10^th February, 2015. Further details will be intimated as the situation emerges.

b)      No forecast has been made by Indian Meteorological Department till date about the above situation.

c)       Our earlier forecast of Mount Fuji eruption during the end of March, 2015 still holds good.

It is requested that on the actual happening of the above incidents, we may be kindly informed so that we may evaluate the efficiency of our Indigenous Hazardous Weather Forecast System.

                                                              Regards

                                                                    GAUTAM MANDAL

                                                         (SWAMI HARDAS FOUNDATION)

   This is the unanimous  e mail sent to me. Let us watch.

Due to W.D, most of N,N-W,N-central India recorded a cloudy and above normal day & night temps on 3-Feb.
RT @ShrivantR: @weatherofindia @delhiweather light fog and min 11.3C in the morning. day is clearing up with sun making an appearance 1:12pm

Rainfall Till 8:30am today...
Jammu = 24.2mm
Vaishno Devi shrine experiences snowfall ... http://ow.ly/IsHiQ 

Present W.D has fizzled out.
Next W.D is expected to affect N,N-W India from Saturday ... http://ow.ly/i/8vvMZ 

An easterlies is affecting S-E,central Tamilnadu coast and S,central Tamilnadu ... http://ow.ly/i/8vuOQ 

12:30pm, Cloudy with moderate rain seen along S-E,central-coast, some interior zones of Tamilnadu ... http://ow.ly/i/8vuSo 

This easterlies moisture push is expected for next 36hrs over S,S-E Tamilnadu !

#Chennai - 1:40pm, a mild day and partly cloudy. Today morning Airport recorded 21.3 C. More 21 C mornings ahead !!

Another easterlies moisture push expected for Tamilnadu coast on Saturday, 7-Feb... http://ow.ly/i/8vvdA