Saturday, May 04, 2019

Monsoon Watch – 3 ...2019 .....4th May
Further Analysis of the parameters as discussed in MW-1,MW-2.
Position as on 4th May :

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. 
wind flow on 4th May 2019



i) In the Western sector Southern Hemisphere, winds are just picking up speed and hitting the East African coast, but no proper re-curving is seen. To get a defined Somali Current, we need a proper re-curving Northwards/North-East of the winds, on the Kenyan coast. The current SST off the Somali Coast is 28 c (above normal),while the required SST in first week of June is 19/20c. (Required to form masses of Monsoon clouds in the warm central Arabian Sea).

ii) In the eastern sector, in the Bay Branch, the cross equatorial winds are currently following the Deep Depression (Fani) 
We prefer the Bay Branch to be better organised, as the normal date for SWM to hit the South Andaman Sea is 15th May.

Mascarene high
 pressure zone in the South Indian Ocean.
Main High reading of 1026 mb and other highs of 1017 mb are currently observed between Madagascar and Australia.




The "Power House" of the Monsoon winds is lower in strength (should be 1032 mb), for this time of the season.

Indicator:-ve. 

 2. Seasonal Low: 

The NW plains heating picked up initially, but stabilised again, as WDs started streaming in.
After the early summer onslaught, the heat decreased a bit over the North and west subcontinent between MW-2 and MW-3 period. Central India went through a heat wave.

Past 7 days anomaly -
North ,west ,central India was in the warm/hot range.





Min temp was in the above normal range.

The seasonal Low, as a result has not improved. Had shown good progress during MW 2.

The pressure in the core region (Thar Desert / Sindh) is just touching 1006 mb. (In 2014 was 1004 mb, 2015 was 1000/1002 mb , 2016 it was at 1002 mb during this time). 

As mentioned, it normally should reach a low nadir of 994 mb in June in the Thar Desert, and with 1008 mb in the South Arabian Sea, a perfect gradient is created to attract the south -west winds towards the coast.

Core low pressure

The highest max temperature (47.5 c) over the subcontinent  was recorded at Khargaon (M.P.) 

After a lull, the minimum temperatures have also increased over the subcontinent and have just started touching the 30 c mark .

Passage of two Western Disturbances along with their induced circulations have caused fairly widespread to widespread rainfall/thunderstorm activity over Western Himalayan Region and isolated rainfall/thunderstorm activity over adjoining plains of northwest India during last week. 
Indicator:-ve. 

3. ENSO: Currently, weak El Niño conditions are prevailing over the equatorial Pacific Ocean and the latest Monsoon Mission Climate Forecasting System (MMCFS) forecast indicates that these conditions are likely to weaken during the summer season. 
 At present, neutral Indian Ocean Dipole (IOD) conditions are observed over Indian Ocean and the latest MMCFS forecast indicates neutral IOD conditions are likely to turn into weak positive IOD conditions during May and June. 

30 day SOI has fallen further after MW2 and is now at  -1.7.
 ( sustained 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. ONI has increased marginally after MW2 and latest value is 0.8 .
( ONI of -0.5 to 0.5 is neutral. Above 0.5 is El Nino, and below -0.5 is La Nina).



Indicator: ENSO should be watched for El Nino development in August/September.

4. The Bay has hosted a Cyclone during mid April. 
As discussed, we should normally see a low sometime after the 15th of April.
 A low pressure area had formed over east Equatorial Indian Ocean & adjoining Southeast Bay of Bengal  on 25th and it had become a Well Marked Low pressure area over the same region during subsequent three hours. It concentrated into a Depression over the same region in the morning on 26th April 2019 and intensified further into a Deep Depression on 27th April 2019. It intensified in to a Cyclonic Storm 'FANI' on 28th th April 2019 and into a Severe Cyclonic Storm in the evening of 29 . It further intensified into a Very Severe Cyclonic Storm in the early morning of 30th April, 2019 and further into an Extremely Severe Cyclonic Storm in the 30th April 2019.
Fani crossed the coast near Puri (Odisha) on 3rd May.

What is needed now is a pulse from the Far East. But,currently there is no storm or low pressure in the Philippines’ Seas.

A strong MJO would hasten the favourable formations and lows, with enhanced precipitation. 
The Madden–Julian Oscillation (MJO) at present lies over Indian Ocean (Phase -4) with high amplitude (more than 1). It is very likely to move in Maritime Continent (phase-5) with high amplitude during next week and in phase-6 during subsequent week.  

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 only sort of  sign is the normal temps (28 c) of the seas surrounding the peninsula. But sea temps (29 c) near the South Andaman Sea are higher.

We prefer the Bay parameters to show fast progress, as the normal date for SWM to hit the South Andaman Sea is 15th May.
Indicator: -ve

5. ITCZ / LWD :
To bring the existing SE winds above the equator (as SW) , the ITCZ should move northwards.Currently it is near the equator. During late April , it oscillated between equator to 5N.

A LWD in the central peninsula region "looks after" the moisture content in the interior areas, and prepares the atmosphere with the humidity required. In reality, this LWD remains till June, in variable phases, and finally merges with the Monsoon trough (axis)/ITCZ  when the ITCZ moves towards the Sub Continent.

Currently, the weak line of wind dis-continuity is located as a trough, through the peninsula, from Madhya Maharashtra towards Kerala.
Outbreaks of pre- monsoon thunder showers which are expected normally in the southern states and South Maharashtra, are not in full vigour yet.

Indicator: Normal


6.Jet Streams :

The 200 hpa Jet streams over the subcontinent is the additional parameter to be watched from MW-3 .

The jet streams are to be followed as the westerly jet core shifts to the north and easterly jet stream is formed, over the course of late summer, progressively from south to north of the subcontinent , heralding the progress of south-west monsoon over the subcontinent.

Currently are weak south-easterly, south of 8 N latitude.
They are required to strengthen to easterlies at those latitudes in the coming days, for heralding the SWM to the South Andaman Sea.



During April,  Sub Tropical Westerly Jet (STWJ): The highest wind speed of 96 kts was recorded over Dibrugarh.

The westerly jet core shifts north of the Himalayas during the southwest monsoon season, as the jet streams turn easterly over the subcontinent.





So, overall, we can summarize as:
PARAMETER
MW-1
MW-2
MW-3 
1) Cross Eq.Winds
Normal
-ve
-ve
2) Seasonal Low
+ve
-ve
-ve
3) ENSO
-ve
El Nino
El-Nino
4) Bay Low
-ve
-ve
-ve
5) ITCZ
Normal
Normal
Normal
6) Jet Streams
-
-
Normal
Overall
Slightly -ve
-ve
-ve



*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 are.


Looking at the current parameters, there seems slight delay in the South West Monsoon arrival dates for Andaman and Kerala as of now. 



South Andamans: 19th May
Andamans Islands : 22nd May

Maldives:  26th/27th May 
Sri Lanka: 30th/31st May

Kerala &NE States: 2nd/4th June.

Coastal Karnatak: 7th June

Goa 8th/9th June

Mumbai  & West Bengal: 12th/14th June.


Monsoon Watch should not be used/depended upon commercially or otherwise. Monsoon Watch Series may differ from other models.

7 comments:

Abhijit Modak said...

Thanks for the update Sir.. was eagerly waiting for the SWM onset dates!

Most of parameters inclined towards negative as of current conditions.. So onset dates look slightly delay with of 2 days at most places but that usually can be consider within normal frame.

Hope current parameters scenario changes and becomes favorable soon for strong onset!

Shreyas Dhavale said...

The advance of the Arabian Sea branch of SWM is also tricky with the likelihood of formation of cyclones due to strengthening of the monsoon onset vortex. It will be interesting to see how things evolve this year given the possibility of MJO being in active phase over the Indian Ocean by the end of May.

Coimbatore Weatherman said...

I'm following your your page since 2012 sir as i found your page through kea blog in tamilnadu and I'm running a weather forecasting page called coimbatore weatherman for tamilnadu people.. i find your page very informative and you guy's are doing a great job in analysing technical parameters required for monsoon watches.

NilaY Wankawala said...

Over the years you have been so acurate in your forecsting that one who follows you would not have to look at even IMD website for onset of SWM and Quantum of rainfall and once season sets in, the forecasting of rainy spells all over India. You are so dependable and perfect in your forecasting and analysis. Thanks for sharing your knowledge through this blog- Appreciaitng your hard work as always-

sset said...

Heat wave catches Tamil Nadu and Andhra Pradesh. Many places 46c +
South East India hottest and dryest place in India.
Cyclone Fani has disturbed many parameters.

Narayanan chennai said...

Sset is right. South east india is getting very less rains and has been a very difficult summer.

sset said...

Continuous NEM monsoon failure, extended SWM, WD, lows always targeting Orissa, NE states is making SE India bone dry. Anantapur, Rayalseema, Chittor, Cudpah 8 years since no proper rain.. agriculture is abandoned!

Posted Saturday night *Mumbai* spotty rains till Sunday as estimated. Saturday city saw 10 mms and scruz 4 mms. Sunday will see some thun...