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 authour is not responsible for any commercial loss from this article, or this series of articles.
Monsoon Watch - 1.. 2014
The Monsoon developments, as they unfold, will be analysed and discussed and explained in Vagaries.
Well well, time flies, and its Monsoon time again ! 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 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. This would be the correct time and jidgment of the Monsoon progress would be simplified at this stage as the ultimate 2 branches are still not formed, and the overall Monsoon "birth" is just taking formation shape.
The Sub-Continent is eagerly awaiting its share of 2014 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.
Weather forecasters are meteorologists, not magicians !
Initially, in the firsr few articles, 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 (Map) During SWM Onset in Early June. and
B)below indiactes the actual situation of the parameters situation today (10th 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 Mascrene 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 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.
1. Cross Equtorial Winds should start forming, and taking shape from mid -April, especially in the South Indian ocean region.
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.
Today, 10th April, we have a strong Cyclone "Ita" to the NE of Australia. (Cat 4). Our concern for the Monsoon formation is to the West...and we have a Low to the West of Australia. Now, we need stronger formations of Highs in the region, and the SSTs in the Southern Indian ocean need to drop further for that.
As on date today, the Mascarene Highs is lacking formation. We see a high of 1019 mb in the map below.., while last year on date 1 segment, of 1034 mb is seen.
Currently the MJO has stalled in the Eastern Indian Ocean region, with the cyclone embedded in it.
For the Bay branch, we have an interaction of a Low off the Western Australian Coast and the MJO, which are "differing" the formation of the SE winds from the South.
Tropical cyclone/ Lows forming in the S.Indian Ocean off the Australian Coast, means a marginal delay in the Mascrene highs strengthening. ITCZ today is around 7S.
Initial forming off the East African Coast, has started from below the equator. and the weak SE flow towards Eastern Africa can be see, though a bit dis-organised.
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,
2. Seasonal Low: Now, this year, the heating in the sub continent has just about started in the Eastern/Central and parts of Gujarat regions. The above normal heating in the NW is yet to start, as March was relatively cooler I would say. The anomaly map for March shows a cooler Central regions and cooler South. This is not much of a plus point in the formation, or a quicker formation of one of the important pre monsoon weather requirement, the seasonal low.
In fact, the minimum night temperatures are still below normal in central and NW India. The current one week into April is also pretty much the same.
The seasonal low, stretch over Arabia thru India, normally starts forming in the Barmer and adjoining regions in the second week of April.
Today, the MSL is around 1010 mb in the Sindh/Rajasthan region. There is a isobar of 1008 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 not upto schedule.
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.
3. ENSO is now Neutral. Last SOI reading observed was -9.0. (It was +9 last year this date !)
Although the El Niño–Southern Oscillation (ENSO) is currently neutral, surface and sub-surface ocean temperatures have warmed considerably, upto 4c above normal (See diagram below ), in recent weeks, consistent with a state of rapid transition.
El Nino conditions may start as early as June 2014 as the SST in the NINO 3.4 has increased by 0.3c in the last 2 weeks.
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 reading for March is -0.71. Thus Neutral conditions prevail for a month . Neutral conditions expected to decrease from June at least. This parameter may disturb the advance and interfere with the date.
Indicator: Towards El Nino.
4. Bay Low: 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 a high sitting in the Southern Bay. The required SW winds may not yet form as yet, as the active trough still around 10S is interacting with the MJO.
But we will see the pulse coming in from The storm Peipah....some hope of a low !
Summary for arrival Date: Parameter 1). -ve. Parameter 2). -ve, Parameter 3) -ve. Parameter 4). Neutral
Tilted towards the negative, as of 10th April.
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 26th April.
There are more parameters are to be considered, as and when they are developed and to be taken into consideration.
Next MW -2 update 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 in 2012..