Saturday, April 09, 2016

Monsoon Watch - 1... 2016
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 for its share of 2016 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 firsr 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.

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 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 yet to form in the required region. Just a small High at 1029 mb. South West off Australia. Four "weak" Lows are tracking in the region. We have to wait for these "lows" to dissipate.

No Tropical Storms around, so no delaying the proper arrangements for a series of Highs. ( Cyclone Zena not likely to disturb the "set up"). 


But things are un-organised  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 SW 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 revolve round a High in the Arabian Sea (normal), 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. Winds are from the East in the Southern Andaman Sea.
Indicator: Normal

2. Seasonal Low: Now, this year, the heating in the sub continent has started from March end , with  Heat Waves in 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 absolutely normal rainfall...29.8 mms received against the normal required of 29.8 mms.. These are a points in the formation, or a quicker formation of one of the important pre monsoon weather requirement, the seasonal low.
Add caption

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 1008/1010 mb covering almost the entire Indian region. In the "core seed" area, it 1008 mb. (The ultimate low in the core, in June when ready, should be 994mb.). This progress is bit tardy. 
Add caption

The current Line of Wind Discontinuity 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). 


The updated (February-March) MEI has dropped from 2.202 (in December-January) to 1.96, for a slightly decreased ranking, now moving towards neutral stage. 


SOI is falling, and is now at - 7.6 ...Now "coming out of the the EL Nino range"..It was -21 15 days ago.


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. The last 3 overlapping seasons show towards establishment of a neutral event. 

ONI latest is 2.0... 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 a 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 East winds. The required SW winds may not yet form at least for the next 3/4 days, as a High is likely to form later this week off Odisha Coast.

Indicator: -ve


Summary for arrival Date: Parameter 1). Normal.  Parameter 2). +ve,  Parameter 3). Neutral Parameter 4). -ve.

Summary: Tilted towards the normal, as of 10th April. Parameters analysed as of now show normal 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 20th. 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.. 


16 comments:

Zohair said...

Siru didnt mentioned about 200hpa jet stream,and a forecast shows 999 hpa seasonal low by 20th

Srikanth said...

As usual clear and lucid Sir. I am no expert but as I see it we could possibly see marginal El Nino conditions persist till May end possibly which is likely to impact the onset. As you rightly point out the bigger worry is the subdued Bay that is likely to play a role in the shift of winds.

Models indicate a fairly strong Tropical Disturbance in the South Indian Ocean around 20th of April http://www.tropicaltidbits.com/analysis/models/gfs/2016040918/gfs_z850_vort_ind_44.png which is likely to prevent the Cross Equatorial trade winds establishing firmly. This is showing in the charts with winds at 850hPa still Easterlies just north of Equator even as late as 23rd / 24th of April.

Early days still will look forward to further analysis from your side Sir.

abizer Kachwala said...

Rajesh sir,if things and all parameters have not structured properly,and the cyclone "FANTALA"which is going to be created in S-W indian ocean around the 20th of april may affect monsoon and cause delay in its onset.isnt it?

Nilay Wankawala said...

Congratulations sir as tidy and as meticulous as ever MW1 is here. Releasing one day in advance and 4 days in advance from last year ( I guess it was 12th April 2015) and 4 indicators thats been followed by you in MW 1 this season, position considering those factors we are right now better than what has been the situation last year same time.
Let's hope as other factors comes to play their role as time progresses, we have a normal monsoon across the india both in quantum and timeliness. Eagerly awaiting all of us here for follow ups with MW series as factors develops and leads you to forecast the date of arrival and quantum later on.

ANOOP RAWAT said...

Last two years there has been too many WD in April and May.what Will be frequency of WD in this summer.

sset said...

From vagaries blogs
parameters as of apr 12 - 2015 MW1
"Summary for arrival Date: Parameter 1). -ve. Parameter 2). -ve, Parameter 3). Normal. Parameter 4). -ve."
Except for first 2 rest seem to be same (for now).

In spite of (2nd parameter -> heating of subcontinent was -ve during 2015 still very good pre - monsoon rains all over india + LWD over southern india + it was el-nino year - 2015 monsoon started much earlier)

As anoop states - WD seems to be getting prominent every passing year

rajesh said...

zohair/srikanth/abizer: I have mentioned in MW-1, that there are other parameters still to be considered. Since some parameters are to be seen and considered in April, they will come up in subsequent MWs...The developments of Lows and tropical storms in the future will be watched, and no comments can be made on the forecasts 10 days away.

Anoop: As the El Nino gradually weakens, the frequency of WDs will reduce.

sset: Parameter 1, which was -ve last year, is linked to rainfall in the pre monsoon period.

rohit aroskar said...

Sir, wonferful and insightful monsoon watch series

sset said...

Thanks Rajesh sir- your MW series educates people all over world unfolds mysteries of monsoon, climate, nature, weather
Actually was wondering independent, dependent variables will be useful for modelling - data scientist.
Today u have given new information to all - parameter1 is proportional to pre-monsoon + relation between el-nino and WDs. NO other blogs nor climate portals have this information.

rajesh said...

sset: Thanks...trying to maximise information and keep it simple (to some extent)

rajesh said...

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Nilay Wankawala said...

Credit Australian government Bureau of meteorology

Latest ENSO Wrap-Up issued 12 April 2016

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

El Niño declining; 50% likelihood of La Niña later in 2016

While the 2015–16 El Niño remains at weak to moderate levels, recent changes in the tropical Pacific Ocean and atmosphere, combined with current climate model outlooks, suggest the likelihood of La Niña in 2016 has increased to around 50%. As a result, the Bureau's ENSO Outlook status has moved to La Niña WATCH.

Temperatures below the Pacific Ocean surface have declined since late 2015, with all but the top 50 metres now cooler than normal. At the sea surface, temperatures have cooled by over 1 °C since their peak, but remain warmer than average and still at El Niño levels. The Southern Oscillation Index and trade winds also show clear signs that El Niño is in decline.

International climate models suggest El Niño will continue to weaken during the southern autumn, returning to neutral levels by mid-2016. By spring, five of the eight surveyed models suggest La Niña is likely, with three neutral. ENSO forecasts made at this time of year tend to have lower accuracy than at other times, with a clearer picture to emerge over the coming months.

La Niña is often, but not always, associated with above-average winter-spring rainfall over northern, central and eastern Australia.
Australia's climate is also being influenced by record warm temperatures in the Indian Ocean. The warmth in the Indian Ocean will likely provide extra moisture for rain systems as they cross Australia during the southern autumn.

ENSO Outlook

Our ENSO Outlook provides
up-to-date information on the likelihood
of an El Niño or La Niña developing.



The status is La Niña WATCH.

Nilay Wankawala said...

SOURCE INDIAN EXPRESS
Published: 11th April 2016 11:05 PM

NEW DELHI: With nine states facing drought like situation in the country, the India Meteorology Department (IMD) has decided to advance forecast for the 2016 Southwest Monsoon nearly by two weeks seemingly to build a positive atmosphere as there is a likelihood of country receiving good rainfall this year.

The IMD for past few years has been releasing forecast in the fourth week of April and the second one in June. But this time it has been decided to advance it as many parts in the country Bundelkhand and Marathwada reeling under acute shortage of water. Last year, the forecast was released on April 22 and in 2014 it was on April 24 and April 26 in 2013.

IMD officials, however, denied advancement of monsoon due to prevailing drought condition in the country.

“IMD has come out with monsoon forecast in mid-April earlier also and there is no specific reason. We are ready with the forecast so we are releasing it,” said a senior IMD official.

Skymet, a private weather forecasting agency, also released its forecast today predicted an above normal Southwest monsoon this year. The forecast of above normal monsoon would augur well for the agriculture sector which is under stress due to two consecutive years of poor seasonal rainfall.

"There is 35 percent chance of above normal seasonal rainfall that is between 105 to 110 percent of Long Period Average (LPA), while there are 30 percent chances of normal (between 96 to 104 per cent of LPA)," the Skymet said in its forecast for this year.

Central India and West Coast are expected to receive a good amount of rainfall while Tamil Nadu, Northeast India and South Interior Karnataka may witness less rainfall, it said.

Nilay Wankawala said...

SOURCE : THE ECONOMIC TIMES
PUBLISHED : 12 Apr, 2016, 04.07PM IST

NEW DELHI: In a major relief for the India's farm sector, India Meteorological Department said the monsoon will be 106% of normal this year. "Monsoon rains will be above long-period average this year and the El Nino conditions will be seen diminishing by June and July," IMD said, adding that it will come out with the second stage of prediction in June.

"The monsoon rains could be above average, as the El Nino weather pattern, which can lead to dry spells in South Asia, is gradually fading and giving way to La Nina," an IMD official said.

The forecast, which comes after two straight years of drought - is likely to boost the farm sector, which has been weighed down by subdued agriculture output and falling farmers' income.

Two back-to-back monsoon failures, 2015 being the hottest year on record, poor post-monsoon rain, an alarming depletion of reservoirs and a heat wave that's forecast to continue and even intensify — all this has changed the country's water economics drastically for farmers, households, businesses and hydropower.

While this year's monsoon is expected to be good, officials say it may take up to three months for water scarcity to ease as soil moisture has dropped sharply.

Depleted reservoirs will take time to fill up to normal levels after rainfall gathers pace in June and July.

Nilay Wankawala said...

IMD HAS RELEASED PRESS RELEASE LRF - 1 and it can be reached at

http://www.imd.gov.in/pages/monsoon_main.php?adta=LRF&adtb=&adtc=&adtd=lrf_1_2016

sset said...

Bangalore soon to touch 40c - +5c above normal. Lack of Trees prime factor

http://www.bangaloremirror.com/bangalore/others/Is-Bengaluru-the-new-Chennai-Avg-temps-have-gone-up-by-5C/articleshow/51785715.cms

City is witnessing another problem - GARBAGE BOMB!!