For higher latitudes, Jet Stream plays an important role in deciding the weather pattern. However for tropics, interseasonal variations are the deciding factor for the weather.
MJO can be determined studying the Outgoing Longwave Radiation OLR depicting Cloud tops temperature and thus forecasting the location of the phase.
The year 2009 turned to be a major rainfall deficiency year for India because of the absence of Enhanced Convection phase of the MJO. In addition to this years where strong deficiency or rainfall was seen in India, MJO wet phase was absent.
Right-
The 2009 plot showing the MJO. On Y-axis, period is plotted i.e months. On X axis, longitudes are mentioned.
Check the vertical column above 70-100E region.
In the map, Orange-Yellow shading indicates suppressed region of rains while the blue shows wet phase of MJO
For the entire year of 2009, there was a remarkable absence of Wet phase of MJO leading to depreciation in the quantum of rainfall
Above-
Two phase of Madden Julian Oscillation in progress. The top image is of 14th May 2011 of the Outgoing Longwave Radiation showing a suppressed phase over India and South East Asia ( Depicted by the brown region in the right side of image)
Bottom image shows the Enhanced phase of MJO depicted by the precipitation region and green blue area over SE Asia. At the same time, the opposite phase can be seen near Atlantic Ocean.
II- MJO Formation
The air flows out from the suppressed convection region due to the absence of primary lifting required for convection. This air progresses towards the Enhanced convection region.
The circulating air carries moisture with it. When it reaches the area of Enhanced Convection,the development of cyclonic circulation at lower troposphere layers ( Around 850mb) leads to convergence of moist air. The moist air rises inside a convection region and hence a Wet phase of MJO develops.
The dry phase of MJO is a region having Cyclonic spin at the 200mb ( In contrast to wet phase mentioned above having an anticyclonic spin at 200mb) while dry phase has anticyclonic or clockwise spin in lower profiles.
This is a textbook description why a broad region ( The Great Whirl mentioned above) is seen during dry MJO in Arabian Sea.
Indian Ocean Dipole
The Indian Ocean Dipole (IOD) is another major contributor in the summer monsoon. The previous years monsoon forecast hadn't mentioned this Dipole but from IndiMO of 2012, IOD will be considered.
The Indian Ocean Dipole also referred as IOD is a variation in the SST ( Sea Surface Temp) in the Indian Ocean. The variations are seen across the Western and Eastern Indian Ocean where above average or below average sea surface temperatures are recorded. Its an aperiodic variation i.e not of a specific duration or is known to repeat after a specific duration. The IOD is a phenomena similar to ENSO ( El Nino Southern Oscillation) in the Pacific Ocean where there is an interaction of the atmosphere and the ocean. Just like the ENSO, IOD has three phases briefly Positive,Neutral,Negative phase.
Positive Phase-
The Positive Phase happens when the SST across the Western Indian Ocean are above normal (Warmer) and the SST across the Eastern Indian Ocean are below normal (Colder). Due to favored SST, strong convection and cyclogenesis take place across the Western Indian Ocean. The rate of this convection activity is often greater than the normal levels for Western Indian Ocean which impacts areas like India,North Africa and Madagascar as shown in the below image of schematic Positive Dipole Mode..
As discussed above, inter-seasonal variation plays a great role in deciding the quantum of monsoon rainfall in India.
ENSO refers to the oscillational transition taking place in the Equatorial Central Pacific due to changes in the Sea Surface Temperatures which is attributed to variations in the intensity of trade winds.
The MJO was mostly positive (+1.5 to 2) all these years especially during the Summer Monsoon period i.e June-Sept
clearly depicting its direct relation.
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_mjo_index/pentad.shtml
It has been observed that the MJO wave has a nature depending on the intensity of Neutral.
those years witnessed more number of wet phase of mjo than the dry
4) IOD-MJO Interaction
The Madden Julian Oscillation is observed widely across the Indian Ocean and Pacific Ocean.
As discussed in the above MJO section, conditions favorable for convection lead to the development of "wet phase" of MJO while those areas where strong convection is not possible the dry phase develops.
It can be noted that the MJO formation across the Indian Ocean is much marked than the Pacific Ocean
The animation of the OLR for a period between 19th Nov-19th Dec 2009 can be seen here at the top panel.
http://www.esrl.noaa.gov/psd/map/clim/olr_modes/mapanim2.html
As seen in the image, a blue shade area which is represented by a "Red Circle" ( Positive phase of the MJO) is forming across East Central Africa while a developed orange-yellow shade ( Negative phase of MJO) is sweeping across Indonesia.
We now have a look at the DMI ( Dipole Mode Index) for the period of Nov-Dec 2009.
DATE DMI
2009:11:11:0 -0.0511759
2009:11:18:0 -0.199991
2009:11:25:0 -0.0942584
2009:12:2:0 0.152676
2009:12:9:0 0.535976
2009:12:16:0 0.571879
2009:12:23:0 -0.0290021
Here, negative DMI indicates Negative phase of the Indian Ocean Dipole (IOD) where Warmer water (SST) is present across the Eastern Indian Ocean and Cooler water is present across Western Indian Ocean.
The Eastern Indian Ocean during a Negative phase has greater convection activity going on which supports the formation of a Wet Phase of the MJO while across the Western Pacific, a Positive ( DRY) phase of MJO develops.
We consider some more examples of a significant MJO event across the region.
OLR Anomaly March 2010-May end 2010
2
For the Western Indian Ocean, one can note that there is a blue shade region ( Blue shade= greater than normal rain/clouding which is the enhanced phase of MJO). An orange shade is noted across the Eastern Indian Ocean ( orange=lesser clouding i.e dry phase of the MJO).
Here is the DMI for the period
DATE DMI
2010:3:3:0 -0.0212098
2010:3:10:0 0.275377
2010:3:17:0 0.378245
2010:3:24:0 0.201978
2010:3:31:0 0.515495
2010:4:7:0 0.712007
2010:4:14:0 0.447102
2010:4:21:0 0.234534
Here, the DMI values are positive ( Positive Indian Ocean Dipole) from 10th March-April end 2010
Thus the Enhanced ( WET) phase of MJO coincides with the Positive IOD.
2) OLR Anomaly (Oct 2010-Dec 2010)
A significant DRY PHASE of MJO seems over the Western Indian Ocean. Lets see the DMI now
DATE DMI
2010:10:6:0 -0.918562
2010:10:13:0 -0.948848
2010:10:20:0 -0.968341
2010:10:27:0 -0.581541
2010:11:3:0 -0.497689
2010:11:10:0 -0.546642
2010:11:17:0 0.0580557
2010:11:24:0 -0.0620495
2010:12:1:0 -0.119381
2010:12:8:0 -0.297918
2010:12:15:0 -0.0470014
2010:12:22:0 -0.493268
2010:12:29:0 -0.0990546
Here, a significant negative DMI event ( Negative IOD) is in place which is responsible for the DRY PHASE OF MJO
More analysis of MJO events with DMI can be done comparing the two links
http://www.bom.gov.au/climate/mjo/ ( OLR ANOMALY MJO)
http://www.jamstec.go.jp/frcgc/research/d1/iod/DATA/dmi.weekly.ascii ( DMI=IOD)
THUS ONE INFERS THAT THE MJO DRY PHASE DEVELOPS WHEN THE NEGATIVE INDIAN OCEAN DIPOLE IS IN PROGRESS WHERAS ENHANCED MJO DEVELOPS WHEN THE POSITIVE OCEAN DIPOLE IS IN PROGRESS FOR WESTERN INDIAN OCEAN. VICE VERSA FOR EAST INDIAN OCEAN
Reason-
As explained in the MJO,IOD section, a positive IOD will support stronger convection and hence Enhanced MJO across the Western Indian Ocean whereas a negative IOD will support suppressed convection and hence a dry phase of the MJO.
The IOD-ENSO relation is still being studied and shall be mentioned in a separate article-
5) Discussion on the present condition
ENSO:
ENSO Neutral conditions are continuing in the Pacific Ocean. After a weak La Nina event in the year 2011 which continued in the 2012 beginning, conditions turned to ENSO Neutral in the Equatorial Pacific Ocean. The latest weekly departure ( Temp.anomaly) from the Equatorial Central Pacific Ocean and surroundings indicate a well defined ENSO Neutral which is persisting!
 |
| NINO REGIONS IN THE PACIFIC OCEAN |
LATEST WEEKLY DEPARTURE ( As of 20th May 2013)
The latest weekly SST departures are:
Niño 4 -0.2ºC
Niño 3.4 -0.4ºC
Niño 3 -0.6ºC
Niño 1+2 -1.1ºC
Above- The SST Anomaly shows positive anomaly regions offshore South America, Australia- Indonesia prominently. However the positive anomaly isn't that significant so as to be considered as El Nino event (prominent departure of -0.4C in Nino 3.4
II ..MJO
As seen from the above index, a negative MJO was persistent during the early to mid may 2013 however, a dry phase is approaching (and now set over 70-100E) region.
III Indian Ocean Dipole
IOD had a strange trend. It remained high (positive) last year from July onwards returning to the mean later on in early 2013 and now having a sharp negative value (-0.61)
IV Somali Current
The above IMD 925mb map showing Somali Jet (current) has established offshore Somali in the Arabian Sea. As the forecast has been late this year, Somali Jet has established (unlike IndiMO 2012 when it wasn't established)
Above is a projection (+7 days) showing amplification of the Somali Jet ( Current). This is an impressive feature which suggests that the monsoon will be approaching ( i.e it doesn't look like a case of stalled monsoon at this level)
V- Low pressure in Arabian Sea
The above parameters look to be normal. However, the short range GFS shows a possibility of development of a low pressure system in the Arabia Sea. This low pressure shall form offshore Yemen coast i.e exactly in the centre of the Somali Jet.
As can be seen from the situation of 30th May/1st June, the system shall be right in between the somali jet and the Indian west coast. This means that if this system intensifies or become more marked, the moisture from the somali jet will be pulled by this system and hence monsoon arrival can get delayed for subsequent west India and Central India also by a few days.
6) 2013 INDIAN MONSOON FORECAST
Its very important to have a look at the ENSO forecast for the Summer monsoon period. Here is the IRI/CPC outlook on the ENSO
IRI Probabilistic ENSO Prediction for NINO3.4 Region
| Season | La Niña | Neutral | El Niño |
|---|
| MJJ 2013 | 21% | 77% | 2% |
| JJA 2013 | 26% | 67% | 7% |
| JAS 2013 | 27% | 60% | 13% |
| ASO 2013 | 28% | 58% | 14% |
| SON 2013 | 28% | 58% | 14% |
| OND 2013 | 26% | 60% | 14% |
| NDJ 2014 | 23% | 63% | 14% |
| DJF 2014 | 22% | 65% | 13% |
| JFM 2014 | 21% | 65% | 14% |
As can be seen from the forecast, ENSO Neutral is likely going to continue throughout the monsoon period! The probability of this more than 50%..
So we conclude that ENSO Neutral conditions will continue in Indian Monsoon
2) Indian Ocean Dipole
WE WILL STRICTLY REFER BOM MODELS/DATA
The Australian Bureau of Meteorology ( BOM) is showing that the IOD will have a mean negative ( negative anomaly) trend during the key monsoon period.. IOD keeps swinging every week ( DMI Values).. However, when a mean is calculated, either a positive or negative value comes in the form of results.
So unlike last year, it looks like IOD will be slightly influencing the monsoon.
MJO
Above is the CPC MJO forecast for June and early July (40 day forecast, base 00z 25th May 2013). The persisting dry phase shall get over around Mid June allowing a wet phase to drive in which will help the progress of the monsoon ( AFTER THE LOW PRESSURE SYSTEM IN ARABIAN SEA AS MENTIONED ABOVE DISSIPATES).
However as IOD is forecasted be to more towards the negative, it looks like a dry phase will be taking up in July. Hence the June 2013 month will witness normal rainfall ( for most of the parts of India)
Conclusion- Neutral ENSO coupled with negative IOD will be dominant in the Indian Summer Monsoon. As a result of negative IOD, MJO might have less wet phases in the season. However it won't bring a large scale deficiency in the net quantum of the rainfall over India!
REGION WISE FORECAST
1) SOUTHERN INDIA
The IOD which is expected to be more towards weakly negative will lead to dry phase development which may reduce the rainfall amount in this area. However, due to favoured conditions, monsoon will follow the dates. The rainfall amounts shall increase from July.
Region will witness " DEFICIENT" Rainfall with around 85% NORMAL RAIN.
2) Western India
The same conditions shall apply for Western India also as if the MJO activity remains less, monsoon winds shall be weak in this region.Also the arabian sea low pressure system will shape up which will cause the monsoon to be slightly delayed here leading to a less June month rainfall (as compared against the normal). However, it has been observed that the monsoon current as well as the quantum intensifies in later July/August which ultimately balances the deficit.
The region will witness "SLIGHTLY DEFICIENT" rainfall around 85% of normal rainfall.
3) Northern India
The region can expect good rainfall unlike the other areas. The primary reason seems to be the wind patterns expected. The region will receive some rains from the Disturbances which may have a southernly dip than normal. This factor was observed in April month also when greater than normal thunderstorm activity was reported across North-East India as the trough dug more southward and brought rains.
Aperiodic rainfall shall be there with 85% NORMAL and 15% DEFICIENT CONDITIONS
4) North East India
NE India will witness EXCESS Monsoon with the primary reason expected to be the less effective Bay of Bengal current.
Expected 100-105% OF THE NORMAL RAINS
5) East India
Region shall witness NORMAL TO SLIGHTLY EXCESS MONSOON CONDITION.
Expected 95% NORMAL
6) Central India
If one assumes the weak monsoon current due to negative IOD and dry MJO, Central India will have a less than normal rains but the rainfall due to low pressure systems will balance the deficit hence the resultant will be NORMAL RAINFALL
rainfall will be 90% NORMAL and 10% DEFICIENT.
7) Andaman and Nicobar Is.
Normal rainfall is expected in this region around 95% of the normal rainfall.
8) Lakshadweep and surrounding
Considering the expected strength of Monsoon current and Ekman Drift this region will witness deficient rainfall
80% NORMAL
2013 MONSOON ARRIVAL DATES
REFER THE MONSOON ONSET NORMS HERE
MONSOON ONSET DATES
-*** NICOBAR ISLANDS AND ANDAMAN ISLANDS ( INCLUDING LITTLE NICOBAR,GREAT NICOBAR,KATCHAL,NANCOWRY ISLANDS AND VICINITY) - MONSOON HAS SET
** PRE MONSOON RAINS WILL INITIATE ACROSS SRI LANKA, SOUTHERN,WESTERN KERALA,TAMIL NADU AROUND THIS MONTH END
*** MONSOON WILL REACH SRI LANKA AROUND 1-2ND JUNE 2013
*** MONSOON WILL REACH SOUTHERN INDIA LIKE KERALA, TAMIL NADU AND SOUTHERN MIZORAM AROUND 1-3RD JUNE 2013
*** LAKSHADWEEP BY 6-7TH JUNE 2013
*** MONSOON WILL COVER NORTH EAST INDIA ( 7 SISTER STATES) BY 10TH JUNE 2013
*** MONSOON WILL REACH CENTRAL KARNATAKA AND MOST OF ANDHRA PRADESH AROUND 10TH JUNE 2013
*** MONSOON WILL REACH SOUTHERN,CENTRAL,WESTERN MAHARASHTRA AROUND 15-17 JUNE 2013
*** IT SHALL COVER MUMBAI BY 16/17TH JUNE 2013
***NORTHERN MAHARASHTRA,SOUTHERN MADHYA PRADESH, CENTRAL GUJARAT,CHATTISGARH ( ALMOST ENTIRE) AND VICINITY BY 21ST JUNE 2013
MONSOON WILL ARRIVE IN NAGPUR ON 19/20TH JUNE 2013 (MEANINGFUL RAINS IN JULY HOWEVER)
*** NORTH INDIA PORTIONS TILL NEW DELHI BY 29TH JUNE 2013 AND PUNJAB AND FURTHER NORTH INDIA AFTERWARDS ( AROUND 3RD JULY OR SO)
*** IT ALL DEPENDS ON THE ARABIAN SEA LOW PRESSURE SYSTEM I.E ITS POSITION AND INTENSITY
*** FORECAST CAN CHANGE DEPENDING ON CONDITIONS. SO PEOPLE MUST FOLLOW UPDATES***
-----------------------------------------------------------------------------------------------------------------------
7) Inference
* METD WEATHER ESTIMATES THAT THE SUMMER MONSOON FOR INDIA IN 2013 (01ST JUNE - 30TH SEPTEMBER) WILL BE AROUND 90% NORMAL AND 10% DEFICIENT (IMD VALUE MAY REACH TO 95% NORMAL I.E DEPARTURE OF -5%)
* THE SUMMER MONSOON 2013 RAINFALL AMOUNT WILL BE ALMOST EQUIVALENT TO 2012 YEAR'S MONSOON
* NEUTRAL EL NINO SOUTHERN OSCILLATION, NEGATIVE INDIAN OCEAN
DIPOLE AND LACK OF MADDEN JULIAN OSCILLATION (WITH MORE DRY PHASE) SHALL REDUCE THE RAINFALL.
* SOUTHERN AND WESTERN,NORTHERN INDIA SHALL GET MORE DEFICIENT RAIN AS COMPARED TO OTHER PARTS. THE LOWEST MAY BE EXPECTED IN LAKSHADWEEP ISLANDS AND AROUND.
* NORTH EAST INDIA WILL GET EXCESS RAINFALL ALONG WITH EAST INDIA GETTING NORMAL OR SLIGHTLY EXCESS RAINFALL.
*MONSOON WILL BE WEAK IN JUNE
* LESSER LOW PRESSURE SYSTEMS SHALL AFFECT THIS YEAR PARTICULARLY IN ARABIAN SEA.
* INDIAN OCEAN DIPOLE (IOD) SHALL REMAIN NEGATIVE ( MONTH WISE) THROUGHOUT THE SEASON.
* ENSO IS EXPECTED TO REMAIN NEUTRAL THROUGHOUT THE PERIOD
* MJO INTERFERENCE SHALL BE WEAK IN BOTH THE PHASES. MORE DRY EVENTS EXPECTED
8) References
1) METD WEATHER - 2011 IndiMO Part I
http://metdweather.blogspot.com/2011/05/indimo-2011-part-i-indian-monsoon.html
2) INDIA METEOROLOGICAL DEPARTMENT- MAPS RELATED TO SOMALI CURRENT
http://www.imd.gov.in/section/nhac/dynamic/nwp/welcome.htm
3) NCEP COLA GFS FOR 850MB MAPS
http://wxmaps.org/pix/casia.fcst.html
4) CLIMATE PREDICTION CENTER FOR MJO RELATED IMAGES
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml
5) JAMSTEC for Indian Ocean Dipole
http://www.jamstec.go.jp/frsgc/research/d1/iod/iod_home.html.var
http://www.jamstec.go.jp/frcgc/research/d1/iod/DATA/dmi.weekly.ascii
6) BUREAU OF METEOROLOGY,AUSTRALIA FOR OLR MAPS
http://www.bom.gov.au/climate/mjo/
7) http://ggweather.com/enso/oni.htm
8) WIKIPEDIA.ORG FOR ENSO RELATED IMAGES
http://en.wikipedia.org/wiki/El_Ni%C3%B1o-Southern_Oscillation
9) METD WEATHER INDIMO 2012
----------------------------------------------xxxxxxxxxxxxxxxx--------------------------------------------------------------
.jpg)
