Sunday, April 22, 2018

Monsoon Watch - 2...2018 ....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 not at all organised.

i) The cross equatorial wind flow, has yet to organise  up in the Western sector Southern Hemisphere. Winds, have not yet in the required SE direction off 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 not organised Westwards towards the Sumatra Coast. Twin Lows at 5N and 5S above and below the Equator between 80E and 90E are kepping the cross flow winds dis organised. The winds hitting Sumatra coast are not Westerly (as required), and also need to gather strength soon.

And that is exactly where the start should be for the SWM to arrive at the Andamans. Upper winds at 100-400 hpa have just about vigorously starting in aiding the lower winds to attain the required direction and strength.

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 1027 mb and another one at 1018 mb 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.Hence would hasten the Cross Equtorial Wind flow.
Indicator : -ve

2. Seasonal Low: 
No meaningful Heat wave is currently observed in the Sub Continent. By Heat waves, we mean temperatures over 5-7c above normal..not the normal heat.


The core low formation region(Thar desert/Sindh) has heated up normally this summer . The highest in the region of Thar /Sindh/Rajasthan has been around 44c, and Vidharbha Chandrapur just about touched 45c on 18/19th April.
See the 7 days Max temperature annomolly 

In 2017, Barmer had approached 46 c and recorded min temp above 30 c. April heat records had 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 had already been recorded in many states of India . Even at Srinagar (Kashmir),Shimla (Himachal) temperatures  approached around 29 c in April 2017 . Delhi AP was 44.9 c on 20th April 2017.

Last year , in 2017,  Most of India was in the 4-7c above normal range and pockets shooting to 15 c above normal ...

Earlier than normal,the night temperatures had 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 April 2017 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.

The seasonal Low, as a result of nominal heating, is shaping up "casually". It has shown slow progress after MW 1 when it was 1008 mb.

Last 2 days, the lowest pressure, in the core (Thar Desert) region was at 1006 mb.(Last year 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). 
IMD Chart:
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 Central-Southern region of the Peninsula…running roughly from Madhya Mah/Marathwada thru Karnataka towards the Kerala Coast. 
Pre –monsoon thunderstorm activity is seen in Interior Mah, Int  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: -ve

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 (Mar/Apr) MEI is at -.502 (in Feb/Mar was -0.731), for a slightly decreased ranking.

SOI rises Sharply from =6.0 in February
30 day SOI has risen , and is now at  10.5 ( 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 -0.77... ( 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.


4. The Bay has yet to host a pre monsoon low during  April. BB-1 had formed way too early in March.
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 normal/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) -ve   2) -ve  3) Neutral   4) -ve   5) Normal.

Summary : Three parameters is -ve as of today . Parameters have not 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 3rd May with Dates of Monsoon Arrival.

14 comments:

Ron said...

Awesome write up.Thank you Rajesh sir for the monsoon watch update

shiekhz said...

Superb work as usual... load of thanx boss

NilaY Rajnikant Wankawala said...

Painstaking detailed indepth analysis as always been done by you sir. Parameters lagging behind as of now. Eagerly awaiting SWM 2018 3rd update.

NilaY Rajnikant Wankawala said...

Credit Australian government bureau of meteorology


Issued 24 April 2018

 

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

 

El Niño–Southern Oscillation expected to remain neutral through winter

 
In the tropical Pacific, the El Niño–Southern Oscillation (ENSO) remains neutral—neither El Niño nor La Niña. All climate models indicate the tropical Pacific Ocean will continue to warm slowly, but temperatures will remain close to average through the southern hemisphere winter.   

 

Most atmospheric and oceanic indicators of ENSO are at neutral levels. Sea surface temperatures in the central Pacific are close to average for this time of year. Beneath the surface, the tropical Pacific Ocean is slightly warmer than average, but well within the neutral range. In the atmosphere, cloud patterns remain weakly La Niña-like, but trade winds are close to average.

 

All international climate models surveyed by the Bureau suggest that sea surface temperatures in the tropical Pacific will continue to rise, but remain ENSO neutral for the remainder of the southern autumn and winter. By September, two of the eight models suggest ocean temperatures may approach El Niño thresholds.

 

The Indian Ocean Dipole (IOD) is currently neutral. Most models indicate a neutral IOD is likely for autumn and early winter. However, three of six models indicate a negative IOD is possible during winter. Typically during negative IOD events, winter–spring rainfall is above average over southern Australia.

 

Climate model outlooks for ENSO and the IOD have lower accuracy during autumn than at other times of the year. Hence current model outlooks for these climate drivers should be viewed with some caution.
 

 

More information


Media enquiries: (03) 9669 4057  media@bom.gov.au
 
Next update expected on 8 May 2018

sset said...
This comment has been removed by the author.
sset said...

Excess bumper rains over MAHA/KONKAN - Mumbai has water supply for next 5 months even if rains fail!

https://www.hindustantimes.com/mumbai-news/mumbai-lakes-have-sufficient-stock-of-water-no-water-cuts-this-summer/story-wF4IRnOD1eKTPR8mVyQlYN.html

Nature balances excess rains with deficit in other regions specially southern states declining rains for last 3 years.

NilaY Rajnikant Wankawala said...

Monsoon has just set in @ vagaries of weather:-)

Abhijit Modak said...

Again someone comparing wrong sub divisions. seems like habit will never go !

Today only Maharashtra government declares drought in 8 talukas from three districts! Links below

https://timesofindia.indiatimes.com/city/mumbai/maharashtra-government-declares-drought-in-8-talukas-from-three-districts/articleshow/63915144.cms

http://abpmajha.abplive.in/maharashtra/maharashtra-government-declared-drought-in-8-taluka-535345

And also Vidarbha region of Maha having less water storage in dams with Amravati division having just 19.2% water left as on today with compare to last year's 25.8% live storage on same date. And Nagpur division having just 17% water left as on today !

Karan Kumbhar said...

Pune recorded a minimum of 16.7 °C on meeting of 26/4/18(IMD data).

This is very rare as it's below normal by 5°C .

sset said...

Abhijit if you see IMD end of monsoon report both SWM + NEM has been deficit / failure since last 2-3 years for south India.
Even South west coast like kerala, Augumbe have been receiving low rains impacting eastern part of south India like TN, south AP- Cauvery never reaches full state...
It is only during pre-monsoon some odd thunders appear.

SWM monsoon always favors Maharashtra, MP, Orissa, Gujarat, Rajasthan leaving other states dry... It may be due to climatic changes, increase forest cover over Maharashtra specially 'KONKAN'... but this is reality

shiekhz said...

Sir, if the low over Tibet strengthen (due to above normal heat) do we see a Positive IOD in coming months??? majority models showing negative IOD

Karan Kumbhar said...

Skymet predicting first cyclonic system in bay could form over next week.
How would that affect the bay parameter sir
Will it likely shift to neutral or maybe even positive ?

ANOOP RAWAT said...

Too humid in Delhi.Sir when will this reduce

ANOOP RAWAT said...

A big Ts hitting Delhi NCR right now

Cyclone Warning for Tamil Nadu & Puducherry coast:  Posted:   15 NOV 2018    Time :   11.00 am IST, 053000 UTC Position of "GAJA...