Severe Weather Forecaster
In continuation to the part I of the 2011 Indian Monsoon Forecast, the PART II is being issued
(c) 2011 METD WEATHER
Its a CHAOS! now happening in the Indian Ocean and part of it in the Arabian Sea. In Mid May when the PART I was being prepared forecast parameters did show a support to a normal and well developed monsoon current by this ( May) month end. However, real time data is suggesting a different scenario
ENSO TURNING NEUTRAL
The El Nino Southern Oscillation after being in the Moderate La Nina stage is finally turning to Neutral Stage which has been confirmed from the Sea Surface Temp data as of Mid May. The peak anomaly in Central Equatorial Pacific was barely -0.77C ( In a very very less region) while IT WAS 0.0C IN MOST OF THE AREA INDICATING THE TRANSITION TO A NEUTRAL STAGE
The present stage is a La Nina Weak to Neutral Stage and I guarantee a 100% chance of ENSO turning to Neutral in June. The effects of La Nina on global scale shall withdraw by June end
** This means that 2011 Indian Monsoon Season will be a Neutral ENSO setup which WAS FORECASTED BY METD WEATHER SINCE EARLY APRIL AND WAS CONTROVERSIAL TO MANY OTHER WEATHER ENTHUSIASTS IN INDIA
The SST data as on May 22 2011 indicates a broad region of Neutral ENSO and poor regions of La Nina
II- Monsoon Current and cyclogenesis-
The Somali Current which looked very good in Mid May has now started fading away and seems to be getting unsymmetrical in nature of flow due to the expected Re-appearance of The Great Whirl or the surface High Pressure region in Central Arabian Sea
This High pressure region or the great whirl shall act as a barrier in the NE progression of the monsoon trough and we might get to see a split flow pattern which means that the monsoon winds and the embedded somali current shall pass through Southern Peninsula of the country into the Bay of Bengal. and with supporting upper level winds in the Bay, the moisture shall cause lots of rainfall in the North East India
Another reason for the prevention on incursion of SW Monsoon into Central India is the lack of a Strong pulling low mechanism ( In Mainland of India or in the Bay of Bengal)
THIS IS ATTRIBUTED TO THE ABENCE OF CYCLONES! The North Indian Ocean Cyclone Season has both positive and negative impacts on the Monsoon.
If a strong cyclone forms within the monsoon trough in the Arabian Sea,it acts as an obstacle to SW Monsoon progression(CASE I) as it disturbs the monsoon current. However, Bay lows provide additional pulling mechanism for the winds and help in the progress (CASE II)
Above Image shows a change in the nature of 925mb winds ( Forecast models) from present period to +168th hour
In the ANALYSIS image, you can notice a divergence wind flow at the Equator just South of Sri Lanka. Its the Inter-Tropical Convergence Zone or ITCZ
In the +168th hr image, you can notice how the low level winds are intensifying over Central India and are boosting in the Bay of Bengal due to a high pressure in Central Arabian Sea ( Can be seen in the area which looks to be the center of this veering winds)
Q. Why is the Tropical activity of this year low?
Tropical Cyclones originate from persisting areas of supportive convection ( mostly isolated thunderstorms areas provided by the Interseasonal Variational Oscillation- MJO) in the large oceans which has SST over 27C, relaxed mid and upper level winds to permit the latent heat release, supportive moisture and convergence ( Movement of air inwards from nearby region to a point in the system) and upper level divergence ( movement of air into surrounding from a point in the system)
This year surprisingly the Madden Jullian Oscillation activity was been a Suppressed Convection* phase of +2.5 magnitude as on 23rd May 2011. This means that broad lower tropospheric circulation at present has a tendency of suppressing convection which is against than that required for cyclones
( * Convection- It is a process of Heat Transfer for a system in non thermal equilibrium which takes place in fluids only)
The Madden Jullian Oscillation waves as in the region of longitude ( 70E to 100E ) which roughly marks the region comprising of Arabian Sea,India and Bay of Bengal showing a strong red part ( Suppressed Convection wave)
This had widely affected the progress of Monsoon as well as inhibited formation of cyclones and other low pressure zones in the seas.
Q. WHAT SHALL BE THE STATE OF MJO IN JUNE?
Forecast models indicating ( Empirical Wave Propogation) that a weak enhanced phase or wet phase shall be slowly moving through the area leading to increase in rainfall activity in southern India during May 28- June 6 2011
This shall also bring some more pre monsoon (PMS) and the monsoon shower in many areas in Southern India particularly Western Coast.
The approaching enhanced phase also is likely to provide the tropical wave ( birthplace of cyclones) by June 5th or so.
Q. Is there any possibility of cyclone in June 2011?
As the tropical wave shall hit Southern Arabian Sea by June first week, an area having severe thunderstorms might flourish into a weak tropical depression *** or a brief low pressure***
The GFS forecasts are indicating this low to make a sweep through Arabian Sea and deflecting away from Gujarat. If this goes true, this will be a CASE I and II AS MENTIONED ABOVE
After this segment, I don't see any setup in the ocean as the suppressed convection phase shall trail behind this wave and inhibit formation of cyclones
*** - Forecast may change with time
Q.If the Cyclone forms, how will it affect the progress of SW Monsoon ?
If GFS is to be believed, I assume that since this cyclone or a broad low pressure will form in the monsoon trough, it might disrupt the progress of monsoon as had been done all the time every year.
It mostly depends on the track of the setup and its separation from the Monsoon Trough. If the present track is to be believed,it shall plum ample rainfall along western India and a bit inside India and then deflect away monsoon winds if it maintains its intensity.
However, if the present track is to be believed, it shall near India thus pulling the SW Monsoon winds.
ESTIMATED QUANTUM/DATES OF SW MONSOON 2011 AS OF 24TH MAY 2011
The PMS shall continue in Kerala,Karnataka in remaining days of May. Due to absence of pulling mechanism right now, Monsoon shall not be keeping its dates for Kerala
The new dates now -
31st May 2011 for Lakshadweep
June 2-3 2011 FOR KERALA,TAMIL NADU
( Pre-Monsoon shower or the Rainfall due to low pressure for West Coast to continue till 9-10th June*** )
Central-Western Karnataka and Goa,NORTH EAST INDIA - 7-8th June 2011
Konkan- 8th to 9th June 2011
Mumbai - 10th June 2011
As the Low shall move towards Omen, it shall pull away winds towards itself and favored by approaching dry phase of MJO, The SW Monsoon progress shall come to a slow stage from 10th June onwards till end of the June
This means that for Southern part of India ( Excluding Andhra Pradesh) rest regions will mark the arrival of monsoon
For most of maharashtra ( Excluding Western Coast), dry weather shall prevail
Dates for Further onset-
Central,Eastern Maharashtra with Andhra Pradesh - NOT EARLIER THAN 30TH JUNE 2011***
FOR NAGPUR- NOT EARLIER THAN 3RD JULY 2011
FOR MADHYA PRADESH- NOT EARLIER THAN 5TH JULY 2011***
FOR NORTH INDIA - NOT EARLIER THAN 10TH JULY 2011***
*** - FORECAST SUBJECTED TO CHANGE WITH TIME***
WITH NEUTRAL CONDITIONS APPEARING IN THE PACIFIC ( NEUTRAL ENSO) THE ACTIVITY OF MJO SHALL REDUCE FROM PREVIOUS YEAR.
MONSOON SEEMS TO BE 80-85% NORMAL
This will be the track due to enhanced MJO and the possible formation of a Tropical low in June
I estimate that due to absence of surface pull
(C) 2011 METD WEATHER