Monsoon Watch - 2...2025 ....21st April
Further Analysis of the parameters 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, are now setting in the required SE direction off the East African Coast. Winds from South East direction as required, are just below the Trough along the 7S line. Above 7S, the winds are Westerlies. 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. "Low" at 5S below the Equator between 80E and 90E are keeping 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.
We prefer the Bay Branch to be better organised, as the SW Monsoon is normally expected there in less than a month.
Indicator: Normal
Mascarene high pressure zones in the South Indian Ocean. Main High reading now 1022 mb and another two at 1024 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 Equatorial Wind flow.
Indicator : -ve
2. Seasonal Low:
Mild Heat wave conditions are currently observed only in the Central Regions of 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 has been around 46c, and Rajasthan, India touched 46c.
Max Temperature departure Anomaly since MW -1
Map of North India borders not correct
See the 14 days Min temperature anomaly
{Previous Performances :
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.
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.}
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The seasonal Low, as a result of nominal heating, is shaping up " Progressively". It has shown progress after MW 1 when it was 1008 mb.
Strengthening of the seasonal low over NW India is required, and a weak Core formation at 1004 mb is seen .
MSLP Chart
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.
{Previous:
2018: The lowest pressure, in the core (Thar Desert) region was at 1006 mb.( 2017 was 998/1000 mb). (In 2011/2014 was 1006 mb, 2010/2012 was at 1002 mb. 2015/2016 it was at 1000-1002 mb).}
The Line of Wind Discontinuity, which brings Pre Monsoon Thunder showers across the Peninsula, is not forming .LWD 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.
Currently Pre Monsoon Thunder Showers are missing
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:
ENSO-neutral conditions are present.. Equatorial sea surface temperatures (SSTs) are near-to-below average in the
central Pacific Ocean and are above-average in the eastern Pacific Ocean.
ENSO-neutral is favored during the Northern Hemisphere summer, with a
greater than 50% chance through August-October 2025.
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.
El Niño: characterized by a positive ONI greater than or equal to +0.5ºC.
La Niña: characterized by a negative ONI less than or equal to -0.5ºC.
By historical standards, to be classified as a full-fledged El Niño or La Niña episode,
these thresholds must be exceeded for a period of at least 5 consecutive overlapping
3-month seasons.
Indicator: heading towards Neutral
4. The Bay has hosted 1 pre monsoon low during 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.
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 above normal normal.
We prefer the Bay parameters to show progress faster , as the SW Monsoon is expected there in less than a month…
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 : Four parameters -ve as of today . Parameters have not improved much compared to MW 1 .
We will put up the estimated date of arrival for Andamans and Kerala 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- 3 up on 1st May with Dates of Monsoon Arrival.
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