NEM Page



Details on the North East Monsoon:

The Northeast Monsoon, also known as the retreating monsoon, is a weather phenomenon that brings rainfall to the southern states of India, particularly the coastal regions of Tamil Nadu, Andhra Pradesh, and parts of Kerala which typically occurs from October to December.

This monsoon is characterized by winds that blow from the northeast, carrying moisture from the Bay of Bengal, and causing rainfall in these regions. It is an important source of water for agriculture in the southern part of India.

SWM onset is well defined, and follows a well coursed out Northward progress. And can be discerned with reasonable accuracy on charts.

For the NEM, it is not so.

In fact, on many occasions, there is no clear indication between the widhrawing SWM and setting NEM. Often one tends to merge into another.
So, setting a date for the commencement of NEM is difficult, and sometimes not possible.

The Northeast Monsoon can give rise to various weather systems and features. Some of the common systems associated with the Northeast Monsoon include:

*The SWM has its origin, its "Power House", is at the Mascrene Highs off Madagascar. The NEM has its origin round a large anti-cyclone over Siberia.

*The Upper winds during the NEM across the Bay are in a clockwise direction.That is an anti-cyclone is formed. At a level of 500 mb, the centre of the anticyclone shifts to central Burma region.

*The Upper Air temperatures show a Northward gradient in the NEM.Near 10N it is normally warmest, and dropping by 8c at 30N.

*Jet streams at 200 hpa are common to both the monsoons.
In the SWM, the Tropical Easterly Jet stream dominates the Peninsula, while the Sub-tropical Westerly Jet Stream is the feature of the NEM.

*The normal Sea Level Pressure during the NEM is a large system of low pressure over the Central Bay. It can extend into the Indian Peninsula as a trough. Towards the end of November, there is a shift southwards of this extended low.

*The general variations and fluctuations in intensity of this low pressure, governs the rainfall. When the trough is well defined, and the low is well marked, rainfall over the southern peninsula is good.

*During the NEM, an occasional burst of cold air from the Siberian High develops a low pressure systems over the Equatorial regions of the South China Seas. These systems move slowly westwards thru Sarawak/Eastern Malaysia coast, and remnants of these cross over into the Bay and form depressions.



*Troughs and Convergence Zones**: Troughs and convergence zones can develop along the coast of southern India during the Northeast Monsoon. These areas of low pressure and wind convergence are favorable for sustained rainfall.

*Divergence over the Ocean: As the Northeasterly winds meet the warmer waters of the Bay of Bengal and the Arabian Sea, they can lead to air rising and divergence, which can result in the development of low-pressure areas and weather systems that bring rainfall to these coastal regions.

*Most of the NEM rains depend on depressions and cyclones from the Bay towards the East Coast of India.

Onset of Monsoon**: The onset of the Northeast Monsoon is usually marked by the arrival of the monsoon winds. Meteorological departments monitor wind patterns and rainfall to officially declare the onset of the monsoon season.



The movement of the ITCZ away from the Indian subcontinent during the Northeast Monsoon season is one of the factors that contributes to the dry and cool weather experienced in the southern and southeastern parts of India during this time. As a result, the ITCZ's position is inversely related to the distribution of rainfall in India, with northern regions receiving rainfall during the summer monsoon, and southern regions experiencing drier conditions during the Northeast Monsoon.

The Tibetan High, also known as the Tibetan Plateau High, is a significant weather feature in Asia. It plays a role in influencing weather patterns not only during the Northeast Monsoon but throughout the year.

During the Northeast Monsoon season, the Tibetan High often has an indirect impact on the weather in South Asia, including India. Here's how it can be related to the Northeast Monsoon:

1. Wind Flow*: The Tibetan High can influence the wind patterns over the Indian subcontinent. During the Northeast Monsoon, the high-pressure system over the Tibetan Plateau can cause a pressure gradient that results in the flow of cool and dry air from the north/northeast towards the Indian subcontinent. This cool and dry air can interact with the warmer, moist air from the Bay of Bengal, contributing to rainfall in parts of southern India.

2. *Rainfall Patterns**: While the Tibetan High doesn't directly cause rainfall, its influence on the wind patterns can lead to the convergence of air masses over India. This convergence can be a factor in the development of weather systems and precipitation, including the Northeast Monsoon.

The Tibetan High, also known as the Tibetan Plateau High, is a significant weather feature in Asia. It plays a role in influencing weather patterns not only during the Northeast Monsoon but throughout the year.

It's important to note that the Tibetan High is just one of several factors that influence the Northeast Monsoon. Local conditions, such as sea surface temperatures, the presence of low-pressure areas over the Bay of Bengal, and interactions with other weather systems, also play a significant role in determining the behavior and intensity of the Northeast Monsoon in any given year.

During the Northeast Monsoon season, the Tibetan High often has an indirect impact on the weather in South Asia, including India. Here's how it can be related to the Northeast Monsoon.

It's important to note that the behavior and intensity of the Northeast Monsoon can vary from year to year, and meteorological agencies closely monitor these systems to provide accurate weather forecasts and warnings.

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NE MONSOON FIGURES FOR 1-10-2014 TO 31-12-2014

SUBDIVISIONS TAMIL NADU AND PUDUCHERRY
TOP FIVE STATIONS ACTUAL NORMAL %DEP
NAGAPATTINAM 1016.2 941 8
KARAIKAL 907.5 1048.5 -13
TIRUNELVELI 847.5 467.2 81
TIRUVARUR 752.6 719.1 5
CHENNAI 719.7 789.9 -9
BOTTOM FIVE STATIONS ACTUAL NORMAL %DEP
TIRUCHIRAPALLI 259.1 391.5 -34
KARUR 258.8 314.7 -18
NAMAKKAL 251.5 291.6 -14
TIRUVANNAMALAI 248.8 446.5 -44
VELLORE 183.5 348.7 -47
SUBDIVISION KERALA
TOP FIVE STATIONS ACTUAL NORMAL %DEP
KOTTAYAM 719.7 535.1 34
ERNAKULAM 647.3 489.3 32
IDUKKI 603.1 564.2 7
KOLLAM 579 638.6 -9
PATHANAMTHITTA 573 624.2 -8
BOTTOM FIVE STATIONS ACTUAL NORMAL %DEP
KOZHIKODE 446.5 422.2 6
KANNUR 383.7 345.1 11
KASARAGOD 363.4 337.9 8
WAYNAD 341.7 332.5 3
PALAKKAD 335 428 -22
SUBDIVISIONS ANDHRA PRADESH & TELENGANA
TOP FIVE STATIONS ACTUAL NORMAL %DEP
NELLORE 368.4 639.3 -42
VISHAKHAPATNAM 353.1 267.8 32
VIZIANAGARAM 294.9 250.5 18
SRIKAKULAM 234 286.1 -18
CHITTOOR 204 362.9 -44
BOTTOM FIVE STATIONS ACTUAL NORMAL %DEP
MEDAK 41.4 110.7 -63
WARANGAL 40.5 119 -66
NIZAMABAD 32 113.9 -72
ADILABAD 31.9 105.1 -70
KARIMNAGAR 17 112.6 -85
SUBDIVISION KARNATAKA
TOP FIVE STATIONS ACTUAL NORMAL %DEP
DAKSHIN KANNADA 341 335 2
BANGALORE RURAL 307 241 27
UDUPI 304 317 -4
BANGALORE URBAN 278 232 20
DAVANGERE 234 177 33
BOTTOM FIVE STATIONS ACTUAL NORMAL %DEP
GULBARGA 78 131 -40
BIJAPUR 77 144 -47
YADGIR 76 153 -50
RAICHUR 73 138 -47
BIDAR 57 121 -53









Saturday, November 15, 2014









NE MONSOON FIGURES FOR 1-10-2014 TO 12-11-2014





SUBDIVISIONS TAMIL NADU AND PONDICHERRY

STATION ACTUAL NORMAL %DEP

NAGAPATTINAM 530.7 432.6 23
KARAIKAL 495.4 521.9 -5
CHENNAI 468 438.5 7
TIRUNELVELI 455.6 268.8 69
PUDUCHERRY 434.5 446.8 -3
NILGIRIS 390.8 314.6 24
TIRUVARUR 360.1 335 7
CUDDALORE 355.9 359.3 -1
TOOTHUKUDI 355.1 249.3 42
DINDIGUL 347.5 275.7 26
ERODE 345 222.3 55
RAMANATHAPURAM 329.1 283.9 16
THENI 322.3 248.2 30
TIRUPPUR 297.9 216.5 38
DHARMAPURI 290.3 233.6 24
SIVAGANGA 290.1 271.8 7
TIRUVALLUR 272.5 337.9 -19
KANYAKUMARI 270.7 346.4 -22
COIMBATORE 267.1 226.6 18
SALEM 266.5 251.4 6
PERAMBALUR 263.3 264.7 -1
THANJAVUR 258.4 292.2 -12
MADURAI 257.2 298.3 -14
VILLUPURAM 245.2 278.8 -12
VIRUDHUNAGAR 243.6 274.3 -11
KANCHEEPURAM 237 365.8 -35
KRISHNAGIRI 217.2 216.8 0
NAMAKKAL 203.5 209.7 -3
KARUR 201.3 206.8 -3
ARIYALUR 197.3 293.9 -33
PUDUKOTTAI 185.1 225.7 -18
TIRUCHIRAPALLI 164.2 242.9 -32
TIRUVANNAMALAI 133.1 278.3 -52
VELLORE 116.2 224.3 -48










SUBDIVISIONS COASTAL AP/R'SEEMA/T'NGANA





STATION ACTUAL NORMAL %DEP





VISHAKHAPATNAM 332.4 232.2 43
VIZIANAGARAM 284.3 214.1 33
SRIKAKULAM 219.5 254.5 -14
NELLORE 189 392.2 -52
GUNTUR 166.7 186.2 -10
CHITTOOR 137 232.7 -41
PRAKASAM 120.6 243.9 -51
KRISHNA 118.6 203.1 -42
EAST GODAVARI 108.9 234.5 -54
ANANTAPUR 107.5 134.9 -20
NALGONDA 101.3 125.8 -20
KURNOOL 97.6 121.3 -20
CUDDAPAH 96.9 180.6 -46
KHAMMAM 94.8 121.1 -22
WEST GODAVARI 73.5 234.3 -69
MAHBUBNAGAR 42 96.1 -56
RANGAREDDY 39.5 103.8 -62
WARANGAL 30.8 102.1 -70
MEDAK 28.1 98 -71
ADILABAD 25.4 91.3 -72
HYDERABAD 23.9 109.8 -78
NIZAMABAD 22.4 101.1 -78
KARIMNAGAR 13.2 97.8 -87





SUBDIVISIONS KERALA





STATION ACTUAL NORMAL %DEP





KOTTAYAM 551.9 423.8 30
IDUKKI 510.5 448.7 14
ERNAKULAM 474.8 380 25
KOLLAM 471.2 492.8 -4
MALAPPURAM 456.5 366.1 25
THRISSUR 438.7 381.4 15
PATHANAMTHITTA 427.8 479.5 -11
KOZHIKODE 406.2 339.2 20
THIRUVANANTHAPURAM 337 382 -12
KASARAGOD 323.6 283.2 14
PALAKKAD 314 345.3 -9
KANNUR 304.6 282.2 8
WAYNAD 267.7 263.8 1





SUBDIVISIONS KARNATAKA





STATION ACTUAL NORMAL %DEP





BANGALORE RURAL 270 203 33
D KANNADA 267 281 -5
UDUPI 252 265 -5
BANGALORE URBAN 250 189 33
RAMANAGARA 196 205 -4
MANDYA 185 180 3
CHITRADURGA 178 134 33
CHAMARAJANAGAR 175 191 -8
TUMKUR 174 174 0
DAVANGERE 169 145 17
CHIKMAGALUR 151 197 -24
U KANNADA 148 176 -16
MYSORE 148 178 -17
HAVERI 145 138 5
HASSAN 138 186 -26
SHIMOGA 127 157 -19
BELGAUM 126 133 -5
KOLAR 126 178 -29
KODAGU 120 239 -50
DHARWAD 107 141 -24
BELLARY 103 134 -23
GADAG 99 138 -28
KOPPAL 97 122 -20
CHICKBALLAPUR 89 185 -52
BAGALKOTE 81 128 -37
YADGIR 64 137 -53
RAICHUR 62 121 -49
BIJAPUR 52 126 -59
GULBARGA 42 115 -63
BIDAR 27 104 -74










OVER 500 MM


OVER 300 MM


OVER 200 MM


BELOW 200 MM









SOURCE IMD CHENNAI





Trough along Extreme South Coast off TN and Sri Lanka with embedded UAC brings in the NEM...19th October

2014

An amateur's attempt at a brief Summary of the NEM...5th October

-The SWM onset is well defined, and follows a well coursed out Northward progress. And can be discerned with reasonable accuracy on charts.
For the NEM, it is not so.

In fact, on many occasions, there is no clear indication between the widhrawing SWM and setting NEM. Often one tends to merge into another.
So, setting a date for the commencement of NEM is difficult, and sometimes not possible.

-The SWM has its origin, its "Power House", is at the Mascrene Highs off Madagascar. The NEM has its origin round a large anti-cyclone over Siberia.

-The Upper winds during the NEM across the Bay are in a clockwise direction.That is an anti-cyclone is formed. At a level of 500 mb, the centre of the anticyclone shifts to central Burma region.
-The Upper Air temperatures show a Northward gradient in the NEM.Near 10N it is normally warmest, and dropping by 8c at 30N.

-Jet streams at 200 hpa are common to both the monsoons.
In the SWM, the Tropical Easterly Jet stream dominates the Peninsula, while the Sub-tropical Westerly Jet Stream is the feature of the NEM.

-The normal Sea Level Pressure during the NEM is a large system of low pressure over the Central Bay. It can extend into the Indian Peninsula as a trough.Towards the end of November,there is a shift southwards of this extended low.

-The general variations and fluctuations in intensity of this low pressure, governs the rainfall. When the trough is well defined, and the low is well marked, rainfall over the southern peninsula is good.

-During the NEM, an occasional burst of cold air from the Siberian High develops a low pressure sysytems over the Equatorial regions of the South China Seas. These systems move slowly westwards thru Sarawak/Eastern Malaysia coast, and remnants of these cross over into the Bay and form depressions.

Most of the NEM rains depend on depressions and cyclones from the Bay towards the East Coast of India.

In my last report on El Nino, we had discussed that El Nino is "on the threshhold" of forming..not yet established.There has been little change from then, as atmospheric indicators continue to hover around El Nino thresholds. Situation is just "little more" than Neutral.

The Southern Oscillation Index (SOI) strengthened over the past seven days, with a 30-day SOI value of -10.0 as on 4th October. Sustained SOI values below -8.0 can indicate El Nino events. Factors favour the formation of a El Nino event within the next 45-60 days.

The overall forecast estimates for the NEM, is mainly depended on the SWM withdrawal, and to some extent the weak MJO after 15th October not "supporting" the fast formation of NEM currents in the Bay. Cooler SSTs are prevailing west of Java and Sumatra.

But, the upper winds are showing signs of "resigning" and changing. The Mascrene highs have lost their grip, and are weaker, and the Tibetan/Siberian High is taking shape,though late .

Anyway, the latest models show the MJO getting weak after 16th October. Its only after 2nd November that the MJO is shown getting stronger (and more effective) in the entire Bay region.

The advent of the NEM may be as a weak current till October end..
Vagaries predicts its advance by the 16th, taking into considerations the withdrawal of the SWM by the 12th.


Excerpts from Shri Das' Book -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------




2013
Posted Saturday Night (4th Jan):

Location of BB-1....9.1N and 82.8E, tracking West/NW....sustained winds at 25 knts and core pressure at 1006 mb...Forecast maintained (as on Current Weather Page)
Heavy Rains likely in Sri Lanka, and then Southern TN...System crossing South of Thanjavur



Posted Saturday 7th Night:

Posted Saturday Night

BB-21 is now "Madi" and a Severe Cyclone,....is located at 11N and 84.3E.
Studying the sub tropical ridge, we see the Southern Limit of the ridge slightly South of 10N, and of course the Northern Limit is in the North Bay. We see a sort of

"absolute no upper wind direction and a sort of stagnancy " in the Western core section of the ridge.
Another HPA and ridge is located over the Indian mainland, though at a lower altitude.
The system is located in the stagnant area of the sub tropical ridge. That is the reason why Madi is almost quasi stationary, and expected to remain with very negligible tracking next 18-24 hrs.
Once it breaks free from the region, it will have a steering guide, and will enter the Western edge of the sub tropical ridge and move NNE. Also the lower level ridge
over the mainland can move East and push the system towards skirting the East Coast.

Some models forecast a Southerly track. It can go the SW way only if it gets "entangled" in the Southern periphery edge of the Sub Tropical ridge, and get pulled SW with the upper winds.

Chennai again gets avoided by another system ! Very little rains accumulating to 20 mms next 2 days.

But,the easterly wave was disrupted by Madi, and is all set to regain strength again from Wednesday off TN coast.




------------------------------------------------------------------------------------------------- Posted 2nd December 2013

Posted on Friday 29th Night:
Overall:
Rains increasing from the TN coast thru into the interior from Saturday onwards. Rain spells will continue thru the next week as an easterly trough sets in with a few embedded UACs. This will culminate as a depression forms in the Bay on the 4th, and approaches the TN coast around the 6/7th of December.

Posted Monday Night:

We can almost continue from Friday's 29th post...The embedded UAC in the eastrely wave has deepened to a WML, BB-21, and lies off the East Coast of Sri Lanka...at 8.2N and 83E.

This, as mentioned in Friday's article, will culminate into a depression.

Chennai (MNBKM) received 43 mms in the day (till 11.30 pm IST) on Monday 2nd, and NGBKM got 12 mms.till 5.30 pm IST..( Actual Average= 4 mms (Sunday), 26 mms ( Monday)... Vagaries had put up 10-15 mms for Sunday 1st and 20-25 mms for Monday 2nd.)

Now, the system BB-21 is expected to track NW, and partially encounter the South TN coast, meaning the Western semi circle, will cross the Southern TN coast.

The sub tropical ridge has shifted a bit towards the East, hence the BB-21, depression, or DD, may track NNE, and skirt the TN coast. Heavy rains will occur along the coastal regions of TN, AP and Odisha as the BB-21 moves NNE.

Kolkata, as mentioned, can get the showers around 8th December...

Chennai: Tuesday: Showers , interspresed during the day...not much amounting to around 10-12 mms.

Wednesday will be windy, with overcast skies and intermittent rain, measuring less than Tuesday..but Thursday will see an increase in intensity. Possibly around 25 mms.


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Posted 24th November 2013






Bangalore Daily Rain for Novembar



Posted Wednesday 11.30 pm IST:

No change...15.5N and 83.8E....and strength a bit more at T 3.8, core pressure 990 mb, winds 50 knts....

Check 17th Sunday's Post on Main Page, the other system shown in the map/diagram on that page has formed...and track seems to be on course as shown....

Posted on Wednesday @ 9.pm IST:

Where is Helen? Almost quasi stationary where it was stated in the last report...at 15.5N and 83.8. In fact stationary for almost 12 hrs now...Winds estimated between 45-50 knots as per DVORAK estimates. Core pressure estimate 992 mb.

Super bands seen uniformly surrounding the centre..unique for this BB-19.



Now onwards, the poleward flow will be resisted by the vertical wind shear, helping in some strengthening of the system.maybe to 60 knts.

But as stated in vagaries in previous reports, the system will weaken a few notches as it nears the coast. Reason: SST near coast is 26/27c...and will not help in the required energy flow continuation...Track maintained as declared earlier.


Next Post here at 11.30 pm IST..



Posted Wednesday @ 3 pm IST:

"Helen" the cyclone was indicated in the morning write up below. Now located at 15.5N and 83.2E, seems to have moved about 55 kms WNW since last posting.

Perfect clouding uni formally wrapped round the centre. But we see upper and vertical shear having a small effect on the system currently. At T 3.3, we see sustained winds estimate (from Sat imagery) at 50 knts (1 minute) around the core. Core pressure estimated at 996 mb

The track currently seems to be West, and heading for Prakasam District, with the centre crossing near by. Heavy rains for Guntur District.


Next Update tonite 9 pm IST



Posted Wednesday Morning 10.30 am IST

BB-19:Continuing its Rapid Intensification trend.

At 15.1N and 83.6E, having tracked W/NW last 6 hrs. Now, at 996 mb and max sustained winds at 35 knts ( 3 mins), it has, as per IMD norms attained the "Cyclonic Storm" Status.Tracking to continue in a Westerly direction.
Uniform convection again seen around the central core. Remarkable system !





As long as any system is over the sea/waters, the wind speed is the dominant critera for gauging its status. On crossing land, the core pressure becomes the main criteria.

Next Update here 3 pm IST.



Posted Tuesday Night:

BB-19, depression moving West, and currently at same position, not having moved. Winds still at 25knts, and core pressure steady at 1002 mb, but potential of deepening in next 12 hrs. Since gusts are touching 30-35 knts, I would expect sustained winds to reach 30 knts by Wednesday, i.e. Deep Depression.

The system may deepen, but show signs of weakening before landfall on 22nd morning.





As seen in the Sat Image with super imposed position of core centre, the core has shifted, or rather the clouds have shifted from the centre as previously seen, and shifted to the Northern semi circle now.


Seeing the convection feasibilities, and the pronounced convective clouding in the Northern Semi circle, it may be possible that the actual precipitation may be more intense in the North of the system centre, even on landfall.



--------------------------------------------------------------------------------------------------------------------------------

Posted Tuesday @ 3.30 pm IST:

BB-19 remains stationary at 14.5N and 85.5E...and at 1002 mb.
However, the Southern quadrant is showing lesser clouds, as winds have decreased to 20 knts and convection decreased. Northern segment winds are maintained at 25 knts.

The depression is likely to gain in the next 12-18 hrs.
Expected to cross AP coast much stronger than projected, but on expected date 21st. Possibly, it may loose marginal strength near the coast, as cross as a DD.
Next Update here at 11 pm IST Tuesday

-------------- ---------- ----------------------- --------------------- ------------
Posted Tuesday afternoon 1 pm IST:

Rapid Intensification !. Thats what BB-19 is going through. Quick developments have deepened the esrstwhile system from Low to a depression, almost by-passing the WML stage ! and having tracked West, is located at 14.5N and 85.5E.

Would still consider it as a depresion with 25 knts winds ( 3 minutes maximum sustained winds), and estimated core pressure at 1002 mb. Presently may not be lower as changes reported from bouys are around 1.5/2 mb/24 hrs.
Some models estimate pressure lower than 1002 mb.

BB-19 is sort of different in the sene that unlike BB-18, or many other WML or depressions, the core is perfectly centred.
Latest example of BB-18 (and other normal systems) usually have an off centre core,and cloudings are normally in the West or SW or NE quadrants. Hence, locating the core centre becomes difficult, and not easy to understand.

But BB-19, as yet, has perfect all round clouding bands in all quadrants, and hence the core centre is in the "centre" itself. It cannot be mistaken for an "eye" as yet.


Next Update at 3.30 pm IST



Bay Low located at 12N and 88.5E on Monday evening..having moved West since last report

The UAC embedded in the trough in Central Bay descends to Sea Level. On Monday morning, it was a Low at 1006 mb located at 12N 90E

Sent By Pradeep John:Rainfall in and around Chennai from Depression BB-18
----------------------------------
in mm (in and around Chennai region) min 30 mm on 17.11.2013

Kolapakkam - 154
Chembarabakkam - 125
Chennai AP (Meenambakkam) - 124
Korattur Anicut - 120
Poonamalle - 120
Madurantakam - 112
Tiruvallur - 110
Tiruttani - 105
Tindivanam - 100
Avadi - 99
Sholinganallur - 94
Poondi - 93
Mailam - 91
Thiruvalangadu - 90
Chennai City (Nungambakkam) - 80
Guindy - 70
Taramani - 70
Pallipattu - 70
Uthireameur - 65
Marina Beach - 65
Cheyyar - 60
Kaveripakkam - 60
Sholingur - 60
Mahabalipuram - 59
Chengelpet - 58
Kancheepuram - 55
Katupakkam - 51
Sriperumbedur - 47
Ennore - 42
Arakonam - 40
Ellapuram - 38
Thamaraipakkam - 35
Cheyyur - 33
Kelambakkam - 32
Katpadi - 30
Ponneri - 30
Kattupakkam - 30

Average approx 72 mms (Vagaries estimate was 50 mms)

Major Rainfall from the Depression from Tamil Nadu
-------------------------------
in mm on 8.30 am on 17.11.2013 (Min 80 mm)

Mayiladuthurai - 220
Kolapakkam - 154
Tiruchi Junction - 144
Trichy AP - 142
Golden Rock - 138
Vandavasi - 130
Tiruchi Town - 121
Manalmedu - 127
Chembarabakkam - 125
Chennai AP (Meenambakkam) - 124
Korattur Anicut - 120
Poonamalle - 120
Lower Anicut - 118
Thiruppanandal - 116
Madurantakam - 112
Tiruvallur - 110
Gingee - 110
Musiri - 107
Karumundaurai - 107
Harur - 105
Tiruttani - 105
Vathalai Anicut - 103
Upper Anicut - 103
Kallakudi - 102
Tindivanam - 100
Pudhucherry - 100
Vanapuram - 100
Avadi - 99
Manjalaru - 99
Pullampadi - 98
Kalrayanhills - 95
Sholinganallur - 94
Uthangarai - 94
Kondampatti - 94
Poondi - 93
Mailam - 91
Pochampalli - 91
Dharmapuri - 90
Thiruvalangadu - 90
Periya Kalapet - 90
Devimangalam - 88
Thogamalai - 87
Lalgudi - 86
Kulthilai - 85
Penucondapuram - 85
Vikravandi - 85
Panchapatti - 84
T.Palur - 84
Thuraiyur - 83
Veernam Lake - 83
Lalpet - 83
Anaikarai Chathiram - 81
Chettykulam - 81
Thuvakudi - 81
Vembavur - 80
Vanur - 80
Tozhudur - 80
Tiruvannamalai - 80
Barur - 80
Yelagiri - 80
Samayapuram - 80
Chennai City (Nungambakkam) - 80


Posted Sunday Night:
Bay will be buzzing again from Thursday,18th: Precipitation resumes for the East Coast from 22nd.

A UAC will form "in situ" in the Bay in the Central region on 18th at around 15N. The UAC will descend to sea level, track Westwards, and cross the East Coast of India in the Southern AP region around the 22nd. Rains very heavy along AP coast and interiors, but good rains all along the coast of TN also. Could be numbered by Tuesday (BB-19).

Hyderabad gets rains on Friday 22nd.

Chennai will get a break in rain intensity from Tuesday thru Thursday.
Friday, 22nd, the rains commence again.

On 21st November, potential Low could form in the SE Bay, South of Andaman Islands in the 7N region. Can have a good potential for further developing possibly upto DD or cyclone stage.

Posted Sunday Afternoon:

NEM effect> Maximum Temperatures and rainfall in Tamil Nadu as on Sunday,17th November morning:

Chennai Meena 25.6c 124 mms, Nungam 26.1c 80 mms, Adirampatnam 26.2c 8 mms, Dharmapuri 24.5c 90 mms, Karaikal 26.3c 20 mms, Tiruchirapalli 23.5c 142 mms, Nagapttinum 24.9c 3 mms, Salem 23c 49 mms, Vellore 23.4c 15 mms and Kodiakanal 12.7.c (That's cold) with 15 mms!!

Rainfall around Chennai Region from Pradeep:
Kolapakkam - 131
Poonamalle - 124
Madurantakam - 97
Chennai AP (Meenambakkam) - 96
Avadi - 96
Mailam - 91
Chennai City (Nungambakkam) - 77
Sholinganallur - 69
Kancheepuram - 60
Cheyyar - 54
Katupakkam - 51
RK Pet - 47
Ellapuram - 37
Taramani - 36
Ennore - 33
Cheyyur - 31
Katpadi - 30

Now, we wait for the projected vortex to form off the coast, as explained in the earlier post..Off shore trough (to host the vortex) is already strengthening.


Meanwhile, as expected, the pulse from BB-18 is tracking West, and will emerge in the Arabian Sea by Sunday Night...more on this in the Sunday night update (10.30 pm IST)



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Posted on Thursday Night:








------------------------------------------------------------------------------------------------------------------
Posted on Thursday @ 2 pm IST

BB-18 deepens to 1000 mb and winds at 30 knts. Apperantly, has moved 30 kms EAST..and is at 10.4N , 85.5E at 12 noon IST...Temporary movement for sure...
BB-18 will send a pulse into the Arb Sea. But when the system crosses TN coast, the clouding will spread into the interior Karnataka and S.Mah regions. Pune will be cloudy then.

Mumbai will also be cloudy with chances of light rain later.

BB-18 will cross by Friday.. We can expect good rains all over TN.
Chennai will get around 50 mms in initial 24 hrs, but Southern coast can expect more amounts.
Patches between Naggi and Kanya Kumari can get over 150 mms Fiday/Saturday

Posted Tuesday Night:
BB-18 has moved West, and is positioned at 11.5N and 85.5E as on Tuesday Night. Having moved 3.7 degrees westwards since Monday Night.... and possibly coming to coast by Late Wednesday Night or Thursday Morning at this rate.
However, system still as WML at 1004 and 25 knts winds...

Posted Monday Night:

BB-18, WML, located as on Monday evening at 11.7N and 88.7E. Pressure 1004 mb, slight deepening. Winds at 20 knts.
Weak convective bands are seen around a circulation centre.
With moderate wind shear (upto 20 knts), and an encouraging Pole ward flow (energy transfer), we see a slight strengthening of BB-18 to a depression by Tuesday evening. System will move Westwards.

Chennai and coastal SST is now 29c, so, we can expect the system to cross Northern TN coast around Chennai by Wednesday. At land cross, near Chennai, winds will be around 35 knts, and rainfall in 24 hrs period will be around 50 mms.

On Wednesday, interior TN will get good precipitation and heavy falls in many districts.
There is a possibility of the pulse crossing into the Arabian Sea, and form a UAC off Karnataka coast by Friday15th.


Posted Monday 11th, afternoon:The system from the Bay is now well marked, and could be numbered as BB-18.
BB-18 is at 11N and 88E, Monday afternoon, and its central pressure is at 1004 mb.
Conditions and parameters will allow it to track Westwards, and deepen to the depression stage by Tuesday. However, precipitation will be restricted to the seas till Tuesday.

On approaching the coast, we see SST resistance to strengthening. Vagaries would slightly modify its last estimate, and estimate BB-18 to cross land at North TN region, and precipitate fairly good amounts ( 40-60 mms) in North TN from Wednesday.

Pulse from BB-18 can form another Low in the Arabian Sea off Karntaka/Goa around 13th.

Another Update tonite by 11 pm IST.
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Posted on Saturday Night at 11 pm IST:

The Low in the Andaman Sea is now positioned at 13N and 93E.
As repeatedly mentioned, we do not want the system to cross the 15N line, and it seems it will not.
Track as per the upper wind indications and shear zones show it moving West, into the warm core of the central Bay. System will then try to veer towards the East-West trough.
But, I observe the seas off the coast are cooler at 28c. The Central bay is currently at 30c.





Indications such as SST and other parameters show the system not strengthening beyond depression, or even WML status on reaching the TN coast (Middle region). At the present rate, should cross the coast around 15th November. Coastal regions start getting precipitation from 14th evening.
Later on 15th, the rains move into the entire State.
Chennai will get the rains commencing from 14th evening.

Detailed Report of Sea Temperature off Chennai as on Saturday:
Current water temperature: 28°C
Last month's average water temperature: 28,6°C
Last month's maximum water temperature: 29°C Fr, 08 Nov, 06:35 GMT
Last month's minimum water temperature: 28°C Fr, 08 Nov, 06:35 GMT
Long term average water temperature: 28,4°C
Long term maximum water temperature: 31°C Fr, 08 Nov, 06:35 GMT

Long term minimum water temperature: 26°C Fr, 08 Nov, 06:35 GMT

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Posted on Friday Night @ 11.45 pm IST:

A Low pressure forms in the Eastern Bay. Currently it is located at 13N and 97E. The adjoining trough will push the Low into the Andaman Islands and will initially deepen. This Low is capable of reaching the TN coast if it cruises South of 15N.
The Low will move Westwards, and bring precipitation to the Bay Islands. If, the system remains South of the 15N line, it would take the Westerly course, and bring rains to the TN coast by the time the cloudings from the system reach the TN coast around the 13th of November.

The system will have enough strength on crossing the TN coast to bring good rainfall in TN from 13th -16th.
In fact, I see the rains moving inland and covering the entire Southern Peninsula. from Wednesday 13th.

Major NEM rains will elude Chennai at least till Tuesday/Wednesday 12th/13th, when, as explained above, clouds and rains from the Low will approach the TN coast.
Chennai rains intensity will increase after 13th/14th for the next 4/5 days.
Nights in Chennai were 22c, and the minimum is expected to be in the 21/22c range this weekend.


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Posted on 6th November @ 11.30 pm IST:
Chennai can get a shower in some parts on Thursday.
Friday onwards, Chennai gets a dry spell, right thru the weekend till Monday.

The Low pressure mentioned in last article, will form around the Andaman Sea on the 9th. Countering weak shear, it will strengthen a bit initially, and move W/NW into the Bay.
Weak MJO conditions now prevail in our seas, and are expected to remain weak for the next 12 days from date.
The system encounters dry anticyclone resistance around the mid Bay region, and in a couple of days after reaching the mid Bay region, can track N/NE. Around 11th November, Dry NW winds will counter the development, but system will survive to move and cross the 15N line.
Would expect the Night temperatures to be around 21/22c in Chennai on Saturday and Sunday.

Totally dry conditions will prevail in the Southern states from this weekend.


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Posted on 4th November @ 11 pm IST

The trough running North South thru the Southern Peninsula (interior) will persist next 3 days. Interior TN and S.I. Karnataka will get the thunder shower in several parts and regions.
Easterly gusts in Kerala and Interior regions have been reported due to the Low and trough in the Maldives region.
Chennai will get the regional thunder shower in different parts of the city next 3 days.
In patches, I would put an accumaulated rainfall of 20-25 mms next 3 days. But,on an average, I would say around 10-12 mms next 3 days. Most of this rainfall on Wednesday and Thursday.

A Low pressure wil move into the Andaman Sea around the 10th of November. The system (will be numbered when required), will move slowly W/NW initially.
Seeing the Current low shear and the forecasted possiblity of shear value, would expect the Low to intensify slowly and move W/NW.
On reaching the Centra/West Central Bay, would expect the system to curve N or NE, due to the upper winds track formation tendency.


Next update on this Page on Wednesday Night.


Posted 3rd November Night...

Low expected to form on 6th around Male (Maldives)..expected to track W/NW...
Chennai received the showers expected for Saturday, with Nunga getting 23 mms and Meena 11 mms (average 17 mms) against forecasted 10-12 mms.
Sunday Night is also seeing Showers in many parts of city.


Page will be updated Monday Night...
Posted on 1st November @ 11 pm IST:

The NEM performance is taken from 1st October, irrelevant of the actual onset date. And this year, the entire TN had excessive rains during the fag end of the SWM.
Hence, the actual October figures are much better than what the NEM has actually precipitated.
Tamil Nadu is deficient by 31% , Chennai is -29%. But Puducherry is deficient by 71%, followed by Thiruvurur at -67%.
Bangalore has received 100 mms, still short by 67 mms. But as expected, Ap has got the distinct advantage of good rains from 2 systems. Hyderabad received 239 mms, which is in excess by 159 mms.

Dipavali this Year in the South:

Since there is a lot of discussion (and hope) on the MJO status, I figure that the MJO is today in neutral phase, and may go into weak phase till 7th November. The OLR map is attached to which one can make his inference.



We see the East Coast off shore trough becoming shorter, and will be off the TN Coast on Saturday, and in all probability, shifting inland on Sunday.

Saturday will see some showers along the North AP coast
Dipavali Day (Sunday) there can be showers "popping" up along the Coast from Nellore to Nagapattinum.

New Years Day (Monday), the rain areas shift Southwards, with the Southern TN coast getting good rains. The Easterly Wave (trough) will be below the 10N line.
Showers in Nilgiri District.

Chennai:
Saturday 2nd November: Chennai will also see some thundery development, and showers in some parts. Rains averaging 10-12 mms.
Dipavali Day 3rd November: Can get another Thunder showers on Sunday. Sunday could see a marginal decrease in rains over Saturday.
Rains decreasing from Monday .

What about Bangalore ? Day will be sunny , but Thunder shower on Saturday evening (around 10 mms) and in some parts of city on Sunday. Decreasing intensity from Monday.

A Low can form in the Andaman region around the 9th of November. It may strengthen initially, but it seems (my views) that it may not get the required energy to gain more.

14 comments:

Krishna said...

NEM will be a failure.
Believe me i have seen time and again when NEM is delayed or weak very rarely it has bounced back to compensate for the deficit.

Worried man from chennai as I expect a crisis ( very severe) after april 2014..

No rain what so ever. The temp looks like that of jan/feb winds are relatively cooler so no chance of rains from the bay.

Thinking of relocation already

regards
krishna

sset said...

It is time weather scientist, geologist study in depth NEM with revision in models. Risk due to continuous failures of NEM and possible desertification of much South east India and Sri Lanka should be taken with at most priority.

Subrahmaniam S R V said...

Deepavali in Tamilnadu was celebrated on 2nd Nov. :)

Subrahmaniam S R V said...

Deepavali was celebrated in Tamilnadu on 2nd Nov. (Saturday)!

Krishna said...

Some sharp showers as expected.
Not substantial though.

Anyway some sporadic showers still happening. With a low expected around end of this week hoping for it to intensity and dissipate as a depression in tn coast. Asking for more i guess

regards
krishna

Narayanan chennai said...

Thank you very much for adding a NEM page. It is a lifeline monsoon for my state.

Narayanan chennai said...

Hi sir will bb19 have effect on chennai

Rajesh said...

Suba Devi: Not a direct strike on Chennai. And i see More precipitation towards AP coast. But Chennai will get heavy showers from the Southern Bands...max impact on AP

Unknown said...

Sir, can you brief about the next seemed to originate near andaman on 22nd november. Will it intensify into cyclone LEHAR and cross Tamil Nadu coast.

Conceptual Persistence said...

You are talking of a easterly wave from December 11th onwards.
Here is a link to the wind anomalies

http://www.atmos.albany.edu/facstaff/roundy/waves/wavemaps/weeks1to2.png

I dont see any easterlies in our neighbhourhood for the next 2 - 3 weeks. Can you correct me if I am wrong ?
Regards,
CP.

Rajesh said...

CP: Please can u mention your name for a one to one chat ? Thanks.
As per my reading, the anomaly chart you showed is for 850 hp winds and OLR. This is basically seen to monitor the MJO.
I have mentioned an easterly wave on the 7th...and would form after the cyclone clears the way. This was put up about 4 days earlier. The cyclone behavior is slow. But, as soon as the cyclone dissipates, an easterly wave is on stream, maybe a day later than anticipated.

Conceptual Persistence said...

I had deliberately not replied to this as I was waiting for your forecast to come true i.e. easterly waves to get set up in the bay of bengal and bring in much needed moisture to my state. But it looks I am right now ? How about you treating me next time I am in Mumbai and if you there is rain from now till December 31st I treat if you are in Chennai ?
CP.

sset said...

2013 best SWM, worst NEM since last 18 years !!

http://www.deccanchronicle.com/131227/news-current-affairs/article/ne-monsoon-tamil-nadu-worst-18-years

Conceptual Persistence said...

Hello Sir,
No sign of any easterly wave and its almost end of year. Don't you think I definitely deserve a treat as I made this prediction on December 10th itself ? I did of course read in the Deccan Chronicle that you had mentioned rainfall to occur in the 2nd week of January 2014. Obviously I will make my prediction on this blog if you give me the permission to do so.
Regards,
Conceptually Persistent Blogger.
:-)

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