Wednesday, April 18, 2012

See Mumbai Page Updated Thursday Morning @ 7 am
NW regions of Sub-Continent are still below the required heat. In sindh /Balochistan (Pakistan) where it is expected to heat up. In India , highest was 44c at Chandrapur, again in central India (as forecasted in Vagaries) , while across the border  we still see the highest at 38c at Chor and Badin on Wednesday. Sukkur was a mild 34c.
And, now A-3 is moving in ! expecting light rains in Karachi Thursday/Friday due to the combined effect of W.D. and trough.

Monsoon Watch - 2


Further Analysis of the parameters as discussed in MW-1. 


1. Seasonal Low: For this parameter, the -ve factor from the previous MW (last week) discussion is maintained, as the average day/night temperatures in the Northern/Central Sub-Continent areas remain in near normal/below normal range.
IMD map of day and night temperature of the 17th anomaly explains this. 







A comparison with previous years shows the difference this year. In 2010, the first 45c was 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, 2011 was similar to this year. This year also, we are yet to reach 45c anywhere in the Sub-Continent, as was in 2011. Into the 3rd. week of April now, and the heat wave is missing.


As on 17th. April, the lowest pressure, in the Thar Desert region is at 1002 mb. (though last year was 1006 mb, 2010 was at 1002 mb this time) and this "low" region is restricted to a small area. As mentioned, it normally should reach a low nadir of 994 mb in June, and with 1008mb in the South Arabian Sea, a perfect gradiant is created to attract the south -west winds towards the coast.


The quick formation of an optimum Seasonal Low due to persistent A-2 (mentioned in the Vagaries' weekly forecast), and absence of heat wave in Central and Northern regions of the Sub-Continent, continues to be un-favourable. 


2. The ENSO is neutral in the Pacific Ocean, with a further warming of the SST in the past 2 weeks. On an average, it is warmer by about 0.1c over the last 15 days. 
The SOI is at its lowest level since early 2010, but remains within values indicative of neutral ENSO conditions. The latest (8 April) 30-day SOI value is −3.8, while end of March was +2.8.




3. Last week, the Cross Equatorial Winds,( Monsoon winds), which originate from the Southern Indian Ocean as SE winds, and cross the equator to become south -west, were weak, and not developed . 


Let me explain, that the winds before  crossing the equator break into 2 branches. 1) gushing into the Arabian Sea, and 2) moving into the Bay of Bengal. 


Today, we find, the winds south of the equator better organised for the Bay branch, in the region south of the Andaman Sea. SW Currents are seen off the Sunmatra coast. And that is exactly where the start should be for the SWM to arrive at the Andamans.


The Arabian Sea branch is still struggling to get organised. Here,  wind speed off the Kenyan coast has maintained the SE flow. But should re-organise fast.


The Mascarene high pressure zones in the South Indian Ocean, at 1030 mb, between Madagascar and Australia, have been observed, and the "Power House" of the Monsoon winds is slightly behind schedule,for this time of the season.


4. 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. 
This parameter, is not very "normal" and tilting towards  "un-favourable" as on date.









I have put up the SST of this year and of last year as on date. Comparison shows it is slightly "un-favourable " around the equator, where the winds turn for the Arabian Sea.


But the pre Monsoon Low in the Bay is still elusive. As discussed, we should normally see a low sometime after the 15th. of April. But as on today, a high pressure region prevails over the Bay.


5. To bring the existing SE winds above the equator, the ITCZ should move northwards. Around 1st. of May, this should cross the equator.  The ITCZ, is in its "normal" position, as of now, at 5S. 


So, overall, we can summerise as:
Parameter:1): -ve. 2): Normal.  3) Normal  4) -ve. 5) Normal.


Most parameters are "Normal" as of today. In today's situation, Monsoon arrival in Kerala could be on normal dates in Kerala and the Bay Islands, and the NE states. 


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 from today when the Monsoon can arrive. Things get clearer by last week of April. Vagaries' (in MW) normally remains true to estimates around early May. 


Next MW up on 25th. April. Quantum will be discussed in the first MW of May.


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9 comments:

Ron said...

Thanks for putting it up...just one question...why haven't you considered IOD in your MW?

rajesh said...

Ron: As mentioned, MW is just analysing the progress to ascertain the date of monsoon arrival.We are just gathering information to see the development strenght to get a rough date of onset. The quantum of rainfall, for which the IOD is taken into consideration (by some forecasters) comes into play in the first week of May, when we start with the quantum of rain.
and I will explain very breifly my method of forecasting in the next MW.
It does not give much importance to IOD. Its not proven yet and quite new..according to me. I have mentioned this in the 2010 MW.

pavan said...

huge amount of rainfall lashing karnataka reports say rainfall upto10cm were reported from the interior yesterday even the sat image
shows clouds over entire region
pl let us knw when pune gets its part

rajesh said...

Pavan: Hosanagara (Shimoga dt)received 10cms as on Thursday morning. And a couple of places 6cms.
I had put up some rain in vagaries' Tuesday forecast for Friday. Should get some rains fri/sat. Around 5-10 mms.
If you have gone thru the MW, you would not rejoice at the rains at this time. Its going to effect the Monsoon.

pavan said...

rain hv to keep ur words, it rained mod in many parts of pune it was heavier in the eastrn parts

Shitij said...

Cloudy weather in Surat.Light drizzle in Surat which lasted only for 5 minutes.Rajesh your forecast was upto the mark. Any more rain for Surat????

PWP said...

Hi Rajesh
Could you tell me about the storm that broke records in Mumbai? I mean, whether it was a Low or UAC? Thanks.

rajesh said...

PWP: Babbarbhai, how are you ? Nice to hear from you. If you are meaning the heavy rainstorm on 26th July, then it was from a local vortex. A local vortex, rising to almost 20,000 feet had created a localised UAC within a small radius around North Mumbai and going about 5 kms further North from the airport. That is near the Vihar lake. The localised UAC was within a trough along the west coast.
Mumbai airport received 944 mms in 24 hrs, actually 18 hrs, and Vihar Lake got 1047 mms.
I shall put up more details to this on Mumbai page when I return from the U.S.
Hope for a good monsoon for our regions.

PWP said...

Hi Rajesh, I am fine. Thank you for your info on Mumbai floods, actually I was trying to find about the cloud mass that moved into Sindh after causing floods in Mumbai, though it did move into Sindh but mostly drizzle/light rain occurred.
Enjoy your trip to the U.S !! :)