Monday, April 10, 2017

Monsoon Watch - 1... 2017....10th April 

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.

The Monsoon developments, as they unfold, will be analysed and discussed and explained in Vagaries. 

The South West Monsoon is just about 35 days away from its normal date of arrival from the shores of India ! Yes ! its just 35 days from the First touch of shores...Southern most point of India on the South Andaman Islands, Indira Point, where the normal arrival date is 15th May.
And its about time we start the follow up of its progress and monitor its developments. 

The Sub-Continent is eagerly awaiting its share of 2017 monsoon rains !

This annual series is a follow up and chasing of the South-West Monsoon. 

Every article in this series explains the synoptic situation as it actually is, and based on the day's position, the date and quantum of rains as on THIS SITUATION.

It is very important to firstly estimate the date of arrival of the S W Monsoon, as year to year, variations in dates of onset of the monsoon can occur and there have been several occasions in the past when the monsoon arrived over certain parts of the country about a fortnight earlier or later than the normal dates. The SWM has the  weatherman tearing at his hair for the exact date or time, extent and progress. This is never 100 per cent sure though various weather models are used to calculate this event.
Initially, in the first few articles, of this series will be chasing and closely following up the actual developments of the monsoon parameters, and analysing its progress regionally for calculating and estimating the arrival date. 

We are not yet contemplating the quantum of rains or the monsoon strength as yet. 

There are 2 parts to this article:
A)-This is the Ideal Conditions  During SWM Onset in Early June.  


and 
B)below indicates the actual situation of the parameters situation today (9th April).

A)
Very very briefly, let  us first understand, that the "power house" of our SWM is actually based far away in the southern Hemisphere. The main "generating factory" is the Mascarene Highs, between SE of the Madagascar coast and Australia. The SWM is born down South, 4000 kms from the Indian Mainland !

The proper formation of these high regions,(1032/1034 mb at least) will boost and create proper SE winds to lash the East African Coast near the Equator, and then turn perpendicular towards SW in the Northern Hemisphere. 

And the formation of the "Tibetan High" is another factor. An anti-cyclone in the upper atmosphere over the Tibetan Plateau. During the formation stages, there will be thunderstorm activity in the SE parts of Tibet during the months of April and May.

To generate a powerful SW wind, the cross equatorial flow must be strong and gusty. SW winds (ultimately upto 600 mb levels) then are capable of riding on the warmer Arabian Sea waters (Arabian Sea Branch of SWM) and bring cloud masses towards the West Coast of India. In the Bay, similar SW winds are generated (Bay branch of SWM), but from SE winds below the equator, just below Sri Lanka.

And to attract the SW winds, again, we need a good proper "seasonal low" to develop in the Sub-Continent. This seasonal low, normally should start forming around Barmer, Rajasthan, by mid April, and at its peak stretch upto Arabia. Seasonal low at its peak, in June, should normally be around 994 mb, and the ridge around Kerala should be 1008/1010 mb. This enables a good gradient to pull the SWM Northwards and inland.

B)-In this initial stage, we will observe the basic root and foundation, the initial 4 parameters only, and the initial seed of the monsoon. From these parameters, later a few more develop.
1. Cross Equatorial Winds from Southern Hemisphere.
2. Seasonal Low over India/Pakistan.
3. ENSO Status.
4. Pre Monsoon Low in the Bay.

Position as on 9th April:
1. Cross Equatorial Winds:
The Mascarene Highs are the main "Power House" of the South -West Monsoons. This generates the South -East winds, which after gaining strength, cross the equator and become south west. For a proper High to form in the South Indian Ocean, the cyclone season (Low pressures) should completely die down from that region.

As on date today, the Mascarene Highs is forming in the required region. A small High at 1031 mb.  Four "weak" Lows are tracking in the region. We have to wait for these "lows" to dissipate.
Two Tropical Storms around, could see delaying the proper arrangements for a series of Highs. 

But things are unorganised  below the Equator.( Wind Chart Below)
Cross Equatorial Winds should start forming, and taking shape from mid -April, especially in the South Indian ocean region. 
Initial forming of SE winds off the East African Coast has started from below the equator. Weak  Westerly  flow below Sri Lanka (in the Southern Hemisphere) can be see, though a bit dis-organised.


ITCZ:This Seasonal trough passes from the South  Arabian Sea to Andaman sea after the withdrawal of SWM in Oct. Shifts further south in Dec. Moves North during SWM
Now near the equator.

Today, the winds  North of the Equator are Northerly in the Arabian Sea, ... and are Westerly South of the Arabian Sea. 
As the Monsoon strikes the Andaman Sea by mid May, developing wind currents ( Westerly) are required to be observed initially near the Eastern side of the Southern Indian Ocean, and this is weakly forming as of today, Southerly flows are striking Sumatra.

Indicator: Normal

2. Seasonal Low: Now, this year, the heating in the sub continent has started from March end , with  Heat Waves in Maharashtra, Gujarat, Central India and parts of NW India.. The above normal heating in many parts continues in April. 
On an average, March has registered normal temperature (average day and night),  

and, with slight above normal rainfall...+7%. These are a points in the formation, or a quicker formation of one of the important pre monsoon weather requirement, the seasonal low.


In June,the seasonal low, which stretches to Arabia from India, normally starts forming in the Barmer and adjoining regions in the second week of April. 

Today, the MSL is around 1008 mb in the North Rajasthan/Sindh region. There is a isobar of 1010/1008 mb covering almost the entire Indian region. In the "core seed" area, it is 1008 mb. (The ultimate low in the core, in June when ready, should be 994mb.). This progress is bit tardy. 


The current Line of Wind Discontinuity (weak in S.Madhya Mah Region) should stabilise around Central India perpendicular down into the Southern Peninsula. 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. 
Indicator: -ve

3. ENSO is on way to a Neutral Stage. 
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 (Jan-February) MEI is steady at -.056 (in December-January was -0.055), for a slightly decreased ranking, now moving towards neutral stage. 

SOI is falling, and is now at  + 5.6.

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... Just marginal, could get lower in the coming months...But at this stage, it cannot be surely mentioned, that an neutral stage could fully develop by June, the onset time of our South West Monsoon.
( 0.5 - -0.5 is neutral. Above 0.5 is El Nino, and below -0.5 is La Nina).

Indicator: Heading towards Neutral.

4. Another pre monsoon seasonal normal requirement is the creation of an initial low in the Bay by the second week of April. This is necessary to trigger off the flow and formation of lows from the bay.
Progress this year is bad, as the Bay shows no signs today. No forecast of any low as of now. (in 2009,a low formed by the 12th. of April, and later it intensified into cyclone "Bijli", 2010 had no low till 3rd week of April).
Today, we have dis organised South winds looping over a  ridge in the Bay. The required SW winds may not yet form at least for the next 3/4 days.
Indicator: -ve

Summary for arrival Date: Parameter 1). Normal.   Parameter 2). -ve,  Parameter 3). Neutral Parameter   4). -ve.
Summary: Tilted towards slightly Negative, as of 10th April. Parameters analysed as of now show slow progress for Monsoon Advance on time.


New Readers, please note, These initial Parameters are normally (every year) considered in MW Series to gauge and estimate the arrival date of SWM, not strength. Time of arrival normally indicated in MW-3, and strength after 27th April. There are more parameters are to be considered, as and when they are developed and to be taken into consideration.

MW-2 on 22nd. April.

While IMD still defers its forecast, IMD should have taken up this job in right earnest much earlier. Vagaries had mentioned this earlier here.. http://rajesh26.blogspot.in/2012/03/importance-of-monsoon-forecast-for.html....March 19th 2012

21 comments:

ugaap said...

Rajeshbhai,

The updated (February-March) MEI is steady at -.056 (in December-January was -0.055),

should read as

The updated (January-February) MEI is steady at -.056 (in December-January was -0.055),

Second point to note is ONI latest is -0.2.

Shreyas Dhavale said...

Very good analysis of the main parameters. Always like to follow the MW series here. Also it remains to be seen if Eurasian snow cover or IOD can impact the monsoon this time or not.

Atul said...

Nice explanation as always :) . Thanks sir. Was eagerly waiting for mw series.

rajesh said...

Thanks Ashokbhai...corrected the Months.

Shreyas: Eurasion Snow cover does effect the Monsoon, especially the March/April cover. It was originally taken as one of the parameters.

Abhijit said...

As usual it's just an amazing experience to watch monsoon unfolding with Vagaries here :)
Very nice detailed analysis covering all main parameters.


Heat wave once again grips North Interior Konkan !!

Some max temp from the region for today(10-04-2017):

Karjat IMD AWS max 43.5°C

Badlapur max temp 43°C with 10% humidity(personal reading) !🔥

With this broken recent made all time record of 42.8c on 27 March 2017. And mine device recorded first ever 43c since started tracking the temp personally from 2012 onward !!

Thane max 41.4°C (Vagarian Ameya Swar reports)

Palghar IMD AWS max 40.4°C

Unknown said...

Nice explanation sir jee.
Hope things get positive for monsoon as days progress

Srikanth said...

Thanks for the detailed post as usual Sir, look forward to the second in the series when we could possibly have better clarity. Looking at long term OLR charts it appears we could see a weak onset for the monsoon though its too early to say as things can evolve in the days to come. Some models indicating a weak disturbance evolving in Central Bay a few days from now though am not sure if it would work as the trigger for the change into Westerlies.

Nilay Wankawala said...

Wonderful analysis as ever been always sir. Your MW series all awaits very eagerly and enthusiasm prevails over revealing and releasing the same. With first part the monsoon season 2017 getting published, curtain has been raised for the entire show to follow up with forecasting vis a Vis performance.

Nilay Wankawala said...

Credit Australian government Bureau of meteorology.

Latest ENSO Wrap-Up issued 11 April 2017

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

 El Niño WATCH continues; eastern tropical Pacific waters warm
The tropical Pacific remains neutral with respect to the El Niño-Southern Oscillation (ENSO). However, there are signs that El Niño may develop in 2017, with the Bureau's ENSO Outlook status at El Niño WATCH. El Niño WATCH means there is around a 50% chance of El Niño developing in 2017, which is approximately twice the normal likelihood.

Sea surface temperatures in the tropical eastern Pacific Ocean have warmed, with the warmth progressively spreading westwards since the start of the year. Additionally, waters in the eastern Pacific subsurface have also warmed over the past few weeks. Waters near the South American coastline near Peru remain warmer than average, which has contributed towards heavy rains and flooding in parts of South America.
 
The pattern of very warm ocean conditions in the far eastern Pacific but neutral conditions overall is unusual. International climate models suggest the steady warming of the tropical Pacific Ocean is likely to continue in the coming months. Seven of eight models indicate that sea surface temperatures will exceed El Niño thresholds during the second half of 2017. However, some caution should be exercised as models have lower accuracy at this time of year, and there remains a significant spread in possible forecast outcomes.

El Niño is often, but not always, associated with below average winter–spring rainfall over eastern Australia and warmer than average winter–spring maximum temperatures over the southern half of Australia. For example, of the 27 El Niño events since 1900, 18 have resulted in widespread dry conditions for Australia.

The Indian Ocean Dipole (IOD) has little influence on Australia from December to April. Current outlooks suggest the IOD is likely to remain neutral at least through to the end of winter.

Next update expected on 26 April 2017

rohit aroskar said...

Nilay..the straight line distance between khar west nd scz observatory is 4 to 5 kms

rohit aroskar said...

Wonderful analysis as always..cheers to MWS

Karan Kumbhar said...

Today's skymet weather forecast mentioned a cyclonic circulation over Andaman sea with potential for development into cyclone. Hopefully this satisfies one of the conditions of MW series.

Nilay Wankawala said...

@ Rohit - noted your replies and thanks a ton for inviting attention.

sset said...


Drought situation worsens over Southern India. Maybe advance warning for 2017 SWM will help for government to wake up? Will it drought again or normal? We understand it is highly complex to predict but maybe models should improve for advance drought forecasts.

http://bangaloremirror.indiatimes.com/bangalore/others/Its-time-to-pray-Unprecedented-drought-turns-out-to-be-much-worse-than-expected/articleshow/58117498.cms

sanjeev Gokhale said...

Thanks sir for detailed analysis in monsoon watch 1. Hope this year monsoon both SWM And NEM are good and remove drought like situations of south. thanks Sanjeev Gokhale Mulund Mumbai

Abhijit said...

Badlapur max temp 41.7°C with 10% humidity today !!

Bit relief compare to yesterday. But still next 48 hrs are crucial..

Atul Naik said...

Always eagerly looking forward to your detailed analysis of the current monsoon parameters. Easy to understand and follow! awaiting the next instalment!

Karan Kumbhar said...

https://www.skymetweather.com/content/weather-news-and-analysis/cyclonic-circulation-forms-in-bay-of-bengal-maiden-cyclone-of-the-season-in-offing/

Vinod Desai said...

Thanks you rajesh sir..The analysis as always easy to understand even for person who does not have any background in meteorology.
It seems the interior region is very hot compared to mumbai(santacruz) since last 3 days. Places like Badlapur, karjat,dombivali, even thane.

Abhijit said...

@ Vinod . Yes just up to 5-7 km inland area from coastal sea face is under influence of sea breeze when it is weak in nature so beyond that area it is most time hot with calm or in N breeze conditions in summer season. So interior Konkan always record high temp by 4-5c than SCZ reading. Even in Mumbai one can feel hot beyond Ghatkopar while traveling toward Thane. So Kanjurmarg,Bhandup, Mulund also can report 40c but no station from there..

Unfortunately most IMD official stations are limited to just Konkan coast like Dahanu, Santacruz, Colaba, Alibaug, Harnai,Ratnagiri, Vengurla,Panaji.. So all this mentioned station are within 5km range from sea shore .. So interior Konkan heat is remained ignored always !!



Only Bhira is single representative from interior Konkan but that too is uncertain as in month will report for just 8-10 days as being part time station of IMD and may be due to improper location setup as media suggest it has pucca surface and is located in Bhira power plant than actual Patnus(Bhira) village so it may be over reporting by to 3-4c higher than actual !

Abhijit said...

Karjat IMD AWS max 42°C today.

Badlapur max temp 41°C with 12% humidity today.

Thane max 39.6°C (Vagarian Ameya Swar reports).

Deonar max 37.4°C (Vagarian Ronnie Bhaumik reports).

Palghar IMD AWS max 36.3°C today.