Sunday, April 20, 2014

Monsoon Watch - 2   (20th April 2014) 
(Request see Article on Big Laptop screen as Maps and Charts will be better Understood and have been put up with lot of effort..Thanks)

Further Analysis of the parameters as discussed in MW-1. 

1. Seasonal Low: As the average day/night temperatures in the Central Sub-Continent areas have  not shown warming up recently, the -ve factor from the previous MW (last week) discussion shows some improvement (though still -ve). A-3 and A-4 have predominantly kept the days cooler. 
Northern India in fact was almost 12-15c below normal in the day.Bengal region still remains above normal.( See Saturday Article below)
Marginal Heat waves are seen in the North East and Eastern coast of India now.
Vagaries' Sunday Map of Anomaly Below

Comparison with previous years-. In 2010, the first 45c touched on 10th. April, and on the same day Nagpur was 44c, Delhi 42.8c. Soon on 15 th April 2010,  Nawabshah (Pakistan) soared to 47c, Simla to 28.2c on 16th, Ganganagar, Akola and Hissar to to 46c. 
But, 2011 ,2012 and 2013 were similar to 2014. This year also, we are yet to reach 45c anywhere in the Sub-Continent, as was in 2011, 2012 and 2013. 
Highest till date ( 2014) is 44c in Nawabshah on 12th April 2014.
Into the 3rd. week of April now, and a prominent heat wave is missing.
The Line of Wind Discontinuity should stabilise around Central India perpendicular down into the Southern Peninsula by mid April. This enhances the speed of the Seasonal Low formation. Normally is required to start taking shape for the monsoon by the second week of April –As on date,  LWD from Central Maharashtra down to Interior Karnataka is forming. Rain/TS have lashed many parts of Central India last 2 days..
In reality, this LWD remains till June, in variable phases, and finally merges with the Monsoon trough (axis)/ITCZ  when the ICTZ moves towards the Sub Continent.
Not much thunderstorm activity in Southern Tibet (though expected to pick up).
Normal April synoptic features :

There is  a high pressure in central Arabian sea and central/north bay which are normal synoptic features seen in April.
But as the second half of summer progresses the high over the bay should collapse (at least by 15th May)  and the formation of low pressures over the Southern Bay should be in situ..
As the second half of summer progresses (by 15th May): Lows over MP, Central India, Chotanagpur plateau(Jharkhand) should become less conspicuous because of the strengthening of the seasonal low over NW india.

As on 20th. April 2014, the core pressure in the seasonal Low, in the Thar Desert region is at 1006 mb, though not prominently formed yet. Could hardly be called a “developing” Seasonal Low.

As on 20th. April 2013, the lowest pressure, in the Thar Desert region was at 1002 mb. (2011 was 1006 mb, 2010/2012 was at 1002 mb this time ).As mentioned, it normally should reach a low nadir of 994 mb in June, and with 1008mb in the South Arabian Sea, a perfect gradient is created to attract the south -west winds towards the coast.

Though the current heating is bleak, some time should be given for the heating to peak (till 1st week of may) , before raising a red flag..
Indicator 1: -ve (last year was also -ve this time of the year)

2. The ENSO:

 Since January, a large volume of warmer-than-average water (known as a downwelling Kelvin wave) has progressed from the western Pacific sub-surface to the central Pacific sub-surface and warmed, eroding the cooler waters in the east.
The latest sea surface temperature anomaly across the NINO3.4 region, in the central Pacific, is +0.3 °C and has shown steady warming since February.
NINO 3.4 is the predominant Region to see for El Nino..For our region.

Nino regions in the Pacific Ocean:

Though currently neutral, all models suggest El Nino conditions through the Indian summer.
Sustained positive values of the SOI above +8 may indicate a La Niña event, while sustained negative values below −8 may indicate an El Niño event. Values of between about +8 and −8 generally indicate neutral conditions.
The latest approximate 30-day SOI value to 6 April 2014 is −9.0.
Last year (2013) the 30 day SOI value was +5.1 (neutral).

Last year was neutral.

Indicator: Towards El Nino ( will interfere with the advance/onset of monsoon  ).

3. Last week, the Cross Equatorial winds, which originate from the Southern Indian Ocean as SE winds, and cross the equator to become South-West, were weak.

Normal wind flow in April: 

The winds on crossing the equator break into 2 branches. 1) gushing into the Arabian Sea, and 2) moving into the Bay of Bengal. 

1) Initial forming off the East African Coast, has started from below the equator and the weak SE flow towards Eastern Africa can be seen.They are becoming organized.
2) In the Bay Branch, Westerlies are forming in the south Indian ocean ,off the Sumatran coast.
We prefer  the Bay Branch to be better organised, as the S W Monsoon is expected there in 25-27 days….

They are better organized than last year on date.
Indicator:  Normal

Mascarene high pressures :

The high has strengthened from 1019 last week  to 1031  mb .
Main High reading now 1031 mb, and 2 more Highs (in the forming) have been observed, one at 1029 mb and another at 1025 mb. between Madagascar and Australia.
Last year (2013) on date the main high reading was 1029 mb and other highs were 1025 mb and 1018 mb.
Indicator: Normal (last year was –ve)   
4. ICTZ : To bring the existing SE winds above the equator, the ITCZ should move northwards. Around 1st. of May, this should cross the equator, and be near the South Andaman Seas around 10th May.
Not much thundery activity in the western Indian ocean .The eastern end sees some Activity.
The ICTZ runs roughly along the 7S line, almost along the entire length from East Africa towards the Southern Indonesian Islands.

Indicator: -ve (last year was normal)         
 5. But the Pre Monsoon Low in the Bay is still elusive. As discussed, we should normally see a low sometime after the 15th. of April. The high pressure region in the Bay, at sea level, no longer prevails.
I do not see much happening soon, as the region does not have the support of a strong MJO. An strong MJO would hasten the favourable formations and lows, with enhanced precipitation. We do not see the MJO wave strengthening till 28th April at least.
Another factor, which helps the winds gain strength, and bring more moisture into the Indian landmass, is the sea temperatures on both sides of the Peninsula. Optimum (warm) temperatures will hasten and create more clouds, and help in faster forming of the lows from the Bay. 
This parameter, is unfavourable compared to last year. See comparitive SST Maps with Last Year

The sea waters are cooler around the Maldives this year.
In the South Indian Ocean, the waters are a bit warmer than last year ,but the Mascarene highs are stronger than last year as already  mentioned above.See comparative Maps below.
Indicator: -ve (last year was normal)               
So, overall, we can summarize as:
1)  Seasonal low:-ve   
2) Enso:Towards El Nino
3)  Cross equatorial winds and Mascarene high : Normal
4) ICTZ : -ve   5) SST: -ve
[Note: the parameters can swing rapidly in short duration as seen in previous years].
Most parameters are Negative as of today.
But, situations can change fast, and by the time we discuss the next MW, some factors can suddenly become +ve or -ve. So, MW discusses and follows the developments as they emerge, and discuss the parameters as is where is.
No model can commit from today when the Monsoon can arrive. Quantum of rain forecasting in the month of  April,  for a period right through September is an impossible task.
Next MW up on 28th. April with Dates of Monsoon Arrival for 1st Phase of Monsoon upto Central India Region
(Last Year (2013), Vagaries had a written Examination cum Learning Curriculum for Forecasting the South West Monsoon. The 2nd Palce with 55% marks was achived by vagarian Rohit Aroskar. This time for MW-2, Rohit's contribution and observations were scrutinised and added to this article.)
These reports are my personal views, study and observations. Estimates and forecasts are also my own calculations and views, and may/may not tally with any other estimates. This may not be used for commercial purposes. The author is not responsible for any commercial loss from this article, or this series of articles.
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Rajesh said...

Vagaries recorded 38.1c on Monday...

Atul P Naik said...

Rajeshbhai: Thanks again for the detailed analysis. Panaji recorded 35C max on Monday (+02), and minimum 26.2C

Rajesh said...

Pune Rains on Monday 21st ..Pics from Pavan on Inter active Page

sset said...

Intense thunderstroms in NAVI MUMBAI. Rajesh sirs Mumbai rains on spot!! Reminds me of 2013 monsoon - Mumbai rains promptly started june 1st week itself (that too with multiples of 200s and 400s mm) and refused to move out till november.

sset said...

seems lots of clouds over NW India- jaiselmar - RAJ again proving lucky low temp put plenty of rains. Guess over last 5 years Western disturbunces have become strons, SW monsoon have become dominant with increased duration BUT pushing poor NE monsoon to almost trickle.

Ron said...

got light drizzles in deonar and chembur at about 9

Anonymous said...

light drizzle and thunder/lighting in thane right now..:)

Anonymous said...

lights rains thunder/lightening in thane right now

Anonymous said...


GSB said...

Light and steady rainfall here in GB road past 10 mins.....accompanied with thunder.....nice drop in temperature...

Rajesh said...

Rains with thunder, light to medium were received in many parts of Mumbai Monday evening and night. While Ghatkopar had heavy showers, Powai,Mulund, Thane received medium rains. Navi Mumbai got thunder showers too.

Rajesh said...

Rains with thunder, light to medium were received in many parts of Mumbai Monday evening and night. While Ghatkopar had heavy showers, Powai,Mulund, Thane received medium rains. Navi Mumbai got thunder showers too.

Abhijit Modak said...

Mumbai see's highest max temp for the current season till today!!

S'cruz max temp 39.0°C & Colaba 36.0°C today..

Hottest Apr 2014 in last 4 years in Mumbai !

Also 2nd Hottest April in last 10yrs as previous highest was 40.6c on 2nd Apr 2009 .. And then current Apr 2014 saw 39c today. Rest Apr were below 39c..

Abhijit Modak said...

Heat wave like condition in North Konkan today !

Some max temp from the region below dated (21-4-2014)..

Badlapur temp 40.0°C with min humidity of 21%.
Thane temp 40.1°C with min humidity of 23%.
Karjat estimated temp 41.8°C with min humidity of 19%.



Prasad said...

Rajesh sir : Give ur prediction for next 2-3 days

Prasad said...
This comment has been removed by the author.
Atul P Naik said...

Panaji records hottest morning temp of 26.8C with RH 80% today April 22. Max temp 34.8C . Hot & stuffy!

Hrishikesh said...

Mumbai at 8pm at 33degree too hot and humid and pressure for first time dropping at night 1008 and dropping and windy winds from west hope a thunderstorm arrives soon

Rawat said...

Suddenly becoming partly cloudy and windy

Rajesh K said...

We have got habituated of your predictions :)

Outlook for next week till Thursday 29th February: Temperatures expected to rise across Maharashtra and Gujarat. Chance of thunderstorms for...