Saturday, April 22, 2017

Monsoon Watch - 2...2017 ....22nd April
Further Analysis of the parameters as discussed in MW-1. 

Position as on 21st April :
1.Cross Equatorial Winds:
Let me explain, that the winds on crossing the equator break into 2 branches. i) gushing into the Arabian Sea, and ii) moving into the Bay of Bengal. 
Normal April Winds

Current Winds

During Monsoon Watch 1 , the cross equatorial flow was weakly forming.

i) The cross equatorial wind flow, has just about picked up in the Western sector Southern Hemisphere. Winds, have not yet achieved the required speeds, but just hitting the East African coast. The Northwards movement of the ITCZ will surely hasten and strengthen the winds.

ii) In the eastern sector,
 in the Bay Branch, the Cross equatorial winds are perfectly diverted and change direction towards SW after just crossing the Equator. Thunder cloud (Cb) developments are seen near the region South of the Equator.

And that is exactly where the start should be for the SWM to arrive at the Andamans. Upper winds at 100-400 hpa are vigorously aiding the lower winds to attain the required strength.
The winds hitting Sumatra coast are not Westerly (as required), and also need to gather strength soon.

We prefer the Bay Branch to be better organised, as the SW Monsoon is normally expected there in 22-25 days…

Mascarene high
 pressure zones in the South Indian Ocean. Main High reading now 1024 mb and another one at 1023mb has been observed between Madagascar and Australia.

The "Power House" of the Monsoon winds is slightly behind schedule, for this time of the season. But it is expected to strengthen fast with no tropical storms around.

Indicator : normal
2. Seasonal Low: 

Heat wave is currently on across North, Central,Western India.
The core low formation region(Thar desert/Sindh) has heated up early this summer . Barmer has approached 46 c and recorded min temp above 30 c. April heat records have tumbled at many locations in the subcontinent. On 19th April 2017, first ever 50 c temperature in April in Asia has been recorded at Larkana (Sindh).
Temperatures of more than 45 c have already been recorded in many states of India . Even at Srinagar (Kashmir),Shimla (Himachal) temperatures have approached around 29 c in April . Delhi AP was 44.9 c on 20th April 2017.

The current temperature anomaly. Most of India is in the 4-7c above normal range and pockets shooting to 15 c above normal ...

Earlier than normal,the night temperatures have also crossed the 30c mark ! Barmer in Rajasthan recorded 30.4c as minimum on 15th April ,Kurnool (Andhra) saw a low of 31 c on 19th morning and Jhansi (UP) saw a low of 31.6 c on 21st morning.

Jaipur,Kota,Bundi,Alwar,Bikaner,Churu,Pilani (Rajasthan), Cuddapah(Andhra) saw lows of/above 30 c on 21st morning.
Comparison with previous years shows the difference this year. 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, in 2011, 2012, 2013 and 2014,
 till date, temperatures were  yet to reach 45c anywhere in the Sub-Continent . 

2015...Into the 3rd. week of April , we had seen 48c in Pakistan on 19th April in Larkana,and 46.5c in Moen Jo Daro. In India had just topped 44.6c in Barmer on 19th April.

2016....touched 46c in Bankura on 16th April...and was constantly hot in Eastern region with almost daily ,a place touching 46c.. Bhubaneshwar and Titlagarh in India and Dadu in Pakistan had touched 46c. Several large regions in Vidharbh, Telengana and MP were in the 44/43c range.

 seasonal Low, as a result of good heating, is shaping up fast. It has shown good progress after MW 1 when it was 1008 mb.

Last 2 days, the lowest pressure, in the core (Thar Desert) region was at 998/1000 mb. (In 2011/2014 was 1006 mb, 2010/2012 was at 1002 mb this time. 2015/2016 it was at 1000-1002 mb). 

Lows over MP, Central India, should become less conspicuous because of the strengthening of the seasonal low over NW india.

As mentioned, it normally should reach a low nadir of 994 mb in June in the Thar Desert, and with 1008mb in the South Arabian Sea, a perfect gradient is created to attract the south -west winds towards the coast.

Thunderstorm activity in Southern Tibet is seen to be picking up. 

The Line of Wind Discontinuity should normally 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.
LWD (trough) is currently near the Southern region of the Peninsula…running roughly from Karnataka towards the Kerala Coast. 

Pre –monsoon thunderstorm activity is restricted to South Karnataka and Kerala. Some activity seen in patches along Coastal A.P. and Odisha…..after  MW 1 release.

In reality, this LWD ( full formed) remains till June, in variable phases, and finally merges with the Monsoon trough (axis)/ITCZ  when the ICTZ moves towards the Sub Continent.
Indicator: normal

3. ENSO: This year also, like last year, we also base our observations on the Multivariate ENSO Index (MEI).  An attempt is made to monitor ENSO by basing the Multivariate ENSO Index (MEI) on the six main observed variables over the tropical Pacific. 

These six variables are: sea-level pressure (P), zonal (U) and meridional (V) components of the surface wind, sea surface temperature (S), surface air temperature (A), and total cloudiness fraction of the sky (C). (Negative values of the MEI represent the cold ENSO phase, a.k.a.La Niña, while positive MEI values represent the warm ENSO phase (El Niño).The MEI is computed separately for each of twelve sliding bi-monthly seasons (Dec/Jan, Jan/Feb,..., Nov/Dec). 

Negative values of the MEI represent the cold ENSO phase, a.k.a.La Niña, while positive MEI values represent the warm ENSO phase (El Niño).

The updated (Feb-Mar) MEI is at -0.08 (in Jan-Feb was -0.056), for a slightly decreased ranking.

30 day SOI has fallen, and is now at  -3.1 ( SOI of -7 to 7 is neutral. Above 7 is La Nina, and below -7 is El Nino ).

The Oceanic Nino Index (ONI) is based on SST departures from average in the Niño 3.4 region, and is a principal measure for monitoring, assessing, and predicting ENSO. After 5 overlapping seasons showing towards establishment of La Nina, we see a neutral turn. ONI latest is -0.2... ( ONI of -0.5 to 0.5 is neutral. Above 0.5 is El Nino, and below -0.5 is La Nina).

Indicator: heading towards Neutral.

The Bay has hosted a pre monsoon low during mid April. 
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.

A strong MJO would hasten the favourable formations and lows, with enhanced precipitation.
But the MJO, it seems will remain stalled (without eastward propagation) for the next 10 days .
Hence, not much progress is expected on this front during the next 10 days.

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. Currently , the sea temperatures on both sides of the Peninsula are below normal.

We prefer the Bay parameters to show progress faster , as the SW Monsoon is expected there in 22-25 days…

Indicator: -ve

5. To bring the existing SE winds above the equator (as SW), the ITCZ should move northwards. Around 1st. of May, this should cross the equator. The ITCZ should now come back to its Northward position, as the effective "Lows" created by the Rossby Wave are reducing. 
ITCZ is just south of the equator (1 s).

Indicator: Normal

So, overall, we can summarise as:
Parameter:    1) Normal   2) Normal  3) Neutral   4) -ve   5) Normal.

Summary : One parameter is -ve as of today . Parameters have improved compared to MW 1 .
We will put up the estimated date of arrival in the MW-3.

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  today when the Monsoon can arrive. 
Quantum of rain forecasting in April for June right through September is an impossible task. Things get clearer by last week of April. Vagaries' (in MW) normally remains true to estimates around early May. 

Next MW up on 2nd May with Dates of Monsoon Arrival.

Major Contribution for this MW by Vagarian Rohit Aroskar.


GSB said...

Great analysis as always Rajesh Sir...

Congrats Rohit for the excellent inputs...we got to see some of them in our WA group....!!!!

Vijith Menon said...

Dear rajesh sir,

El nino is forecasted to strike again after July - your thoughts on this and effect on the monsoon.

Srikanth said...

Good Read Rajesh Sir, looking at some long term models there appears to be some issue with CEW with some parts of Arabian Sea seeing Easterlies even as late after 20th May though as you rightly say things could drastically change.

Nilay Wankawala said...

What a painstaking effort to give readers scenario of earlier years too so that comparison becomes painless for readers. Your work always carry your signature abd by reading one can make out its Rajesh sir write up. Congratulations sir.

In MW 2 Factors have turned up better than what they were Under MW1. Let's hope things would turn even better as time unfolds itself.

sset said...

Thanks to Rajesh sir for great Monsoon Watch series -> evergreen information....

Very interesting article....
Finally Karnataka wakes up. Reliability of IMD mathematical models are in question? KAR is looking for its own models..

In the last 16 years, Karn­a­taka has faced drought for 13 years. But in all these years, national reports, drawn from Indian Meteorological Department (IMD) data, have said that monsoon was either normal or above average. (for example 2016 IMD failed massive southern Indian drought)

Cumulus Arjun said...

Rajesh sir, can you predict the time of the onset of monsoon over the west coast. Will it be early this year or late as usual?

rajesh said...


Arjun: Wait for MW-3

Vijayanand said...

Great detailed analysis

emkay said...

Great refresher as usual from Rajesh Sir.
Was on a quick official visit to Mumbai Fri/Sat. Got some time to enjoy the feeble sea breeze late evening on Marine Drive. Seems the peak dry heat has abated. But humidity levels are below par for the month I suppose.

rohit aroskar said...

Thanks GSB sir

Dattaraj Joshi said...

Great analysis Rajesh Sir.

It would be nice if you can put some kind of comparison graph between Vagraies prediction V/s actual arrival dates(for last 5-6 years) of monsoon in MW-3.

And similarly for MW-4, comparison of prediction V/s actual of overall rains

Abhijit said...

Great MW-2 presentation as usual from Rajesh Sir.. And amazing detailed contribution from Rohit.

Current WD has disturbed the heat low.

rohit aroskar said...

Thanks Abhijit

Vinod Desai said...

Hello sir,
I will be visiting patan(North Gujarat) between 2 may - 6 may. How would be the weather there during that time. At present temperatures are below normal.

Nilay Wankawala said...

Credit Australian government Bureau of meteorology .

Latest ENSO Wrap-Up issued 26 April 2017

The latest ENSO Wrap-Up and Climate Model Summary are now available on the Bureau's website.

ENSO neutral, but tropical Pacific waters continue to warm

The El Niño–Southern Oscillation (ENSO) remains neutral. However the Bureau's ENSO Outlook is currently at El Niño WATCH, meaning there is around a 50% chance—twice the normal likelihood—of El Niño developing in 2017.

Tropical Pacific sea surface temperatures (SSTs) have warmed since the start of the year. SSTs in the central tropical Pacific are now 0.5 °C warmer than average, still below the +0.8 °C threshold for El Niño levels. Atmospheric indicators of ENSO remain firmly neutral, although the Southern Oscillation Index (SOI) has returned to negative values over the past fortnight.

International climate models suggest the tropical Pacific Ocean is likely to continue warming in the coming months, though in recent weeks some models have reduced the expected extent of warming. Five of eight models indicate that sea surface temperatures will exceed El Niño thresholds during the second half of 2017, a reduction of two models since the last Wrap-Up release. It should be noted that models have lower accuracy at this time of year.

El Niño is often, but not always, associated with below average winter–spring rainfall over eastern Australia. Of the 27 El Niño events since 1900, 18 resulted in widespread dry conditions for parts of Australia.

The Indian Ocean Dipole (IOD) is currently neutral. Four out of six climate models suggest a positive IOD is likely during winter. When a positive IOD coincides with El Niño, the typical El Niño dry signal expands, and generally stretches further west over eastern and central Australia.

Next update expected on 9 May 2017

Vijayanand said...

Good rain in mysore and KGF area's on Tuesday evening.
In bangalore most area's got drizzle for 1 hour and infact the only place with heavier rain was the cricket ground. Which led to IPL match being cancelled. Cricket grounds and rain, there is some correlation ...hahahha

Atul Naik said...

Excellent and detailed analysis as always. Thank you Rajeshbhai and Rohit. A necessary reading every year for all those, who are trying to understand the intricacies of SW Monsoon!

rohit aroskar said...

Thanks Atulji..MWS is a wonderful legacy created by Rajesh sir

rohit aroskar said...

* legacy in creation..