Wednesday, July 21, 2010

Analysis of Strong Rainfall anomaly in India in 2010 Monsoon season

In local aspects of temperature, pressure and moisture, I don't find any snag thats preventing rainfall from not happening in the required quantity. The situation similar in appearance to the present was in late june- july period when the SW monsoon winds were not directed towards the main land as Phet had diverted the strong flow though some moisture was pumping in due to surface lows over Rajasthan and North central India. Then a organised low in BOB which swept across central India reaching Saurashtra in few days regulated the monsoon winds....

I have been using other models such as the Indian Ocean Dipole, ENSO appearance and the most important movement of MJO
I think you must be knowing the significance of Indian Ocean Dipole or Dipole mode index DMI in Summer Monsoon season or SW monsoon season.. The concept of IOD is similar to that of El~Nino and La Nina but IOD happens in Indian ocean only
A strong negative DMI means comparitively warm waters are present near Indonesia then near West Indian Ocean causing greater than avg rains in Indonesia and lesser than avg rains in India. 
There was a strong anomaly or Negative DMI in June reaching upto -0.8C.... Since it was an el nino year, less rains were expected by me but also I was and am hopeful to see an overall 65% normal rains or 35% deficient this time
The IOD is recovering and as per datas on early july it was 0.2C+
DMI now will rise causing good rains in India if there are no other barriers as such.. A significant negative IOD happened in 2009,2008 and Positive in 2007 which was the La nina year... 
Try to compare the annual rains for this year

(2)-- ENSO
El Nino Southern Oscillation has now transformed to a La Nina as being depicted by SST datas. 
This means the trade winds from East to west have now become strong and will likely push warmer water saturated near Indonesia to Western Indian Ocean thus rising the SST and helping for a Positive phase of IOD. 
During El Nino, trade winds weaken and local winds West-East push warm water to Indonesia causing Negative IOD

This year's La Nina coupled with developing positive IOD can result in better rains in August and some days of September as per my forecasts which I had made in May 2010.

(3) Madden Jullian Oscillation-MJO
MJO is a travelling rainfall anomaly across the Pacific and Indian oceans.Positive MJO helps in developing Severe Cyclones too. It was a +2 in June and it was a Cat.4 Phet which also was calculated by me in May
Right now, A good 2.0 cell looks travelling here. As of 16th July its near 140E and its a cool or negative MJO phase for Oceans around India so less rains.

(4) Monsoon trough shift
    Though I can't assure whether such thing has happened or not as I hadn't seen the positions of Jet streams over India after May end. The last time I had seen was before my travel to Ladakh to check the weather there.I think this year no significant Jet streams had reached India which c'd had prevented the trough shifting northwards.. IF no jets build, trough usually shifts north causing less rains in Kerala and central portions..

In all, I will expect a good rainfall in 2011 if La nina stays good and in August and some days in September 2010

Akshay Deoras,
P- 94223-13055

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