Interesting days ahead as rain could make a return later this week

Rain is expected to be back later this week if forecasts then out to be true. Latest Cola prediciton is for around 150 mm on 28/29/30. We need to follow closely to see if a revival is on the cards for Chennai.

1,025 thoughts on “Interesting days ahead as rain could make a return later this week

  1. Rao, to be honest i am not an expert on SoI and its impact on our Bay
    of Bengal and so i can not participate in your post. You are one of the
    pillars of this blog. sometimes too much technicality will not get
    attracted by new comers. Too me i always appreciated your work.

    Even Ashok patel sir posted ur model and quoted u. I too told Ashok patel sir that we have great guys like him in our blog. We and sri too have talked about your model but we always say that it has to be studied with more examples, than here and there citations.Wait for your time. In 2010, nobody will even reply to my comments.But now everthing has changed. People will come to know who has knowledge and who is bluffing.

    Today a small kid is putting MAB model without understanding the
    influence points. We have to guide them. If we put some corrective
    commets, it is upto the bloggers to take it in good sense and learn. We
    cannot teach who is stubborn. If they react then we have to leave them.

    We are not experts in everthing. You are in SoI. i know about heavy
    rainfall, GTS cyclone….it goes on. we can learn from each other. When
    GTS posted a cyclone dynamics, i am sure including me, 99% did not
    understand what he posted yet people liked his comment. It includes me

    People like some style of some bloggers. Eg. Kamal has great
    acting skills and his movies are beyond comparison. But Rajini movies
    dont have any acting skills, yet people like his style and he is loved
    more than kamal.

    You have to put examples of more cyclones or take few years and tabulate with MJO and SoI along with landfall point. Then no one can doubt your model. My doubt is always how can SOI differentiate landfall in a small area such as BOB. How can it show central TN or South AP. The influence area is too small.

    Please continue. Credit always comes with hardwork. I give my thumbs up for ur dedication, hardwork and sticking to your point even after taking so much questions from guys like me who are not experts in SoI.

    • Thanks ur supporting and encouraging words PJ. These words speak ur maturity in mind set up.

      Definitely SOI is very big parameter. So error point will be more if we consider small BOB size compared to big size of the earth. So at the interface of the SOI phases, we can have +/- 1 correction value in SOI.

      For example a cyclone with +1 or -1 can cross either of the side of NTN or SAP. This is applicable to all other phases of SOI.

      • Hi rao,
        learnt a lot from you on these topics but still coming to terms on these…keep going….

  2. LPA In SW bay, any chance for rains in Chennai? Also could someone tell me, what is the status of ridge around the NTN.

  3. Rsrao… Even though I rarely get time for blogging , I am following your comments so regularly and most impressed by ur predictions and just to add guest11k, sel, gts and PJ to this list,
    I miss vinoths and sri comments as well. Its been a lot of learning from all.
    Keep ur good work. Keep going friend

  4. flash news in sun tv…
    upper air circulation over Andaman and Nicobar….
    heavy rainfall warning all over tamilnadu (STN,NTH,AND COASTAL TN)

  5. Everybody(CMC,NAVGEM,GFS,GFS PARALLEL) expects arabian sea circulation to develop other than ECMWF..
    Let’s see which one gets it right..

  6. I don’t know if experts noticed this.
    CFS expects boxing day system to happen!!!! πŸ˜€
    but Still a long way to go though.

  7. rami, really sorry if u hav taken anything to heart.. i never ignore anyone’s post if it has any valuable content and also i never self claimed or proclaimed me as a steering expert or any kind of expert here.. i shld say a big thanks to all of u here especially our vinod.. learning is a continous process..what i say thru blogging is thru repeated observation for the past few years.. cyclone steering is a complex and dynamic process involved with lot of feedback mechanism.. i always think of explaining tis here but i dont knwfor some reason it dint happned..anyway i will say my point here now,, soi is one of the parameter tat indicates upper trop str along with important equatorial trough but how it impacts the realtime movement of a weather system remains a question wich is never explianed in the blog.. upper trop str dip in latitude is reflected in soi but soi never explains the strength of the influencing ridge,shape of the ridge.. just an example to say.if soi values r determined by upper str position with latitude, look into tis one where the soi numbers remains same in all 3 cases as the str is seen along 15 TO 17N but the track is different in all 3 cases. and system falls poleward of the 200 hpa ridge,equatorward of the 200hpa ridge, on the ridge ,inside the ridge..

    look into tis case where system falling inside the ridge ,in tis case soi will be above -10, but the position where the system falling matters wich cannot be explained thru soi ..see this two examples str dip is same in two cases but the track is completely different.. i hav already said tis here but u said mjo is king so it will do ..wen i see the track irrespective of mjo , u say soi is the will do.. tats y i said i am not into tis theory of mjo soi anymore.. it is quite easy to track the system by following the contour of lpa ,hpa around the system,streamlines of the ridge around by considering the system intensity and wind shear direction.. make it simple and enjoy blogging.

    • Sel, we are here for learning. I never said MJO alone do miracle or SOI else do miracle. I always try to interpret based on both MJO & SOI co-ordination.

      One more thing how we can interpret definite Landfall point that too only with 500-200 hpa stream lines as we don’t have any super computers in our hand.

      Even super computer holding weather agencies continuously getting failure in our BOB-season.

      So started MJO & SOI concept after observing sine 2005-yr, laid the foundation during 2002 & 2004 AP-drought years due weak-Elninos

      • whomever it may be..nature has its own course wich cannot be predicted well in advance. lot of assumptions with past 6 hours data is fed into computers to derive the output.. realtime output is nearly impossible as the parameters wich r considered as input changes often.. for tis reason ,there comes the ensemble track. they derive the output by varying the inputs keeping the initial run till the end.. tis is superior but still error do happens.

  8. Onset of NEM 2014 Phase-III getting more n more confirmed day-by-day..Massive towers in Foreca’s forecast..Expecting an avg of 8 cms before 29th. Instead of a dumping deluge, it should be a slow and steady one for 3 days..Somewhere between 12 to 15 cms from this 3-4 days spell should be really good.

  9. Open challenge on lighter note πŸ™‚

    If any single blogger here if interpret a cyclone’s Landfall point with “+/-1 latitude point” based on stream lines (use any sort of parameter), then i will stop cyclones’ track interpretation based on MJSOI-model.

  10. I appreciate the work of Mr Rao, i rarely blog but i keenly watch the blog. Proud of you all and Mr Rao. If we cant appreciate each others scientific interpretation , atleast refrain from finding faults. I have sailed on ships , where a fraction of error in the compass can make the ship reach cuddalore instead of chennai. With limited data , Mr Rao has given lots of innovative ways of approaching weather studies. Science needs to be approached from different angles and experimented.Healthy arguments have always contributed to progress. Wish MR Rao and Selvan Fun to have fun in their work. We enjoy both of your works.

    • agree. see each one has their own style in interpreting. but i never find faults without any reason.. i hav told many times i am keeping away myself from tis theory as i said tis openly months before. but again i was pulled into this for not getting convinced to it.. if the person is not convinced to str theory, and so he/she moving to new theory .. same applies to me and i really dont know y i was targetted yestrday..

  11. Selva,

    Based on steering pattern in 500 hpa, we can draw probable LF points indicated by arrows. But system can end at one point if it was successful system.

    Then how to fix LF value based on today’s 500 hpa stream lines?

    • This problem doesn’t arise if we understand MJO & SOI probabilities based LFs.

      We can rule out all the probable scenarios except 2 probable LF points well in advance.

      • I am going to dump this unorthodox MJO & SOI concept as its failing to the expectation.

        So I would like to go back towards Orthodox steering style based on stream lines. Trying to learn LF points based on steering patterns.

        For this reason asking the above question how to predict/estimate LF-point based on stream lines in advance? Here we are trying to learn new concepts. Nothing wrong in it.

      • Ok got it.

        That’s why ensemble forecasts are developing to get less error. Overall its not easy to predict a cyclone’s track, especially in our boss of bay (BOB) in advance.

    • One important point double vorticies literally making dilema systems.

      Even this “double vorticies” phenomenon existed in south Indian cyclones too.

  12. Yesterday cyclone Rami or tropical storm rao, lashes the blog around midnight with winds gusting upto 200+ kmph with torrential downpours exceeding 300mm + at many bloggers

  13. Flash News,

    1. MJO strong in Phase 3 and entering into Phase 4 by month end.

    2. Cyclogenesis probability by December 1st is confirmed.

    More prospects for North TN when MJO enters Phase 4,great end to November expected.
    This movement of MJOwill trigger more convection from west pacific.

    SOI too increased to -7.58 from -7.96. This too good for NEM
    to bounce back.

  14. Vorticies if consolidated at the black circle (figure), then it will target at least CTN even if it follows N/NW track.

    But unfortunately 500 mb vorticity not becoming strong, which is really worrying factor. Instead negative vorticy (more blue in color) can be seen at the circle in 500 mb vorticity diagram. Even for 99w and 91B, this 500 mb vorticity created problems.

    Even for a tropical disturbance to become a depression, 500 mb vorticity has to deepen. But 700 & 850 mb vorticies are in good shape (but with disturbing neighboring vorticity at Arabian ocean side).

    Figure: 500 mb vorticity:

    850 mb vorticity:
    700 mb vorticity:

  15. Rsrao,

    the reality is, when SOI was within -5 the nem onset happened and then started to pour, once SOI started decreasing below -5, then rain stopped over NTN, but still STN is getting good rainfall.

    I still feel that the ENSO strengthened to 0.7C as per last report a week back, this should effect later stage for us, this ENSO condition should bring good precipitation to us.

    rami you would remember that we are taking Augus and September conditions of ENSO, SOI, NAO and IOD, like that when ENSO strengthens in November first week, then it should reflect towards TN by late November or December.

    Do you agree with me?

    • I agree.

      But If ENSO strengthens above 0.5 then corresponding Indian ocean factor IOD has to become +ve (above 0.5) for better monsoonal rains (either SWM/NEM). Or else If IOD doesn’t become +ve, then SOI has to be either within normal range (-8 to +8 according to BoM)

      Reason is simple:
      Monsoon needs mositure transport/feeding either from IOD based mechanism or SOI-based trade winds. MJO/Kelvin/Rossby/Mixed rossby alone suppoer the tropical conection for longer duration.

      • To understand this concept we need to pull the rainfall data for “Elnino coupled with -ve IOD”. In the last 100 yrs only 1 or 2 yrs this combination occurred. We need to see the SOI values for those yrs.

        We don’t have any big problems in the moisture transport mechanism in other combinations of ENSO & IOD. One factor get be compensated by other factor.

  16. ECMWF has also been a reliable model amidst all these confusions.
    See how this model is showing 2 LPAs in BOB and Arabian on 29th Nov.Add the fact that MJO will add some serious clouding,we are assured of rains.It is definitely not a system..Just a LPA at best

  17. Thiruvarur district got battered yesterday… Thiruvarur city alone clocks 6cms.., and nagai too slowly regaining strength ….look out for copious December… King of NEM

  18. latest satellite picture shows dense cloud mass east of triconmalee, srilanka. from here the system might deveop and move towards north tamil nadu coast. if it goes below pamban, no use for northern districts beyond nagapattinam. conditions are however continue to favour good rains across whole north tamil nadu & south andhra in another 36 hours. from now.

  19. models predict th system may intensify upto wml or depression only…othen than that impossible….track also from commorin to nagapattinam……above nagai chanes are low

  20. a mild circulation seen in the latest satellite picture. now it looks like moves little bit north east and centered around east of Jaffna by 300 to KMS. it has to pick up and take north westerly track and at present it is placed in a right position to get more rains for north tamil nadu. north of nagapattinam. this sytem looks like may not bring any rains to south tamil nadu below pamban as per the latest picture. any way next 36 hours are crucial.

  21. we need a deep depression and takes longer time to cross coast and also to travel north to bring useful, heavy rains for chennai.

  22. we are in need of rain especially over the catchment areas of drinking water lakes of chennai, the lake levels are pathetic even less than last year level

  23. circulation is seen over 7 North & 85 east. – south east of triconamalee, srilanka – around 400 KMS. and 500 KMS from pamban. ideally placed to cover chennai as well in a day or two.
    JTWC would come up with their report soon.


    ♦ The upper air cyclonic circulation over south Andaman sea & adjoining southeast Bay of Bengal now lies over
    Equatorial Indian Ocean and adjoining southeast Bay of Bengal and extends upto 1.5 km above mean sea level.
    Under its influence, a low pressure area may form over southwest Bay of Bengal around 25th November.

    Forecast from 27th

    ♦ Increase in rainfall activity over south peninsular India.

  25. The Southern Oscillation Index (SOI) continued to drop during the past fortnight before rising slightly after reaching βˆ’13.3. The latest 30-day SOI value to 16 November is βˆ’10.9. Sustained positive values of the SOI above +8 may indicate a La NiΓ±a event, while sustained negative values below βˆ’8 may indicate an El NiΓ±o event. Values of between about +8 and βˆ’8 generally indicate neutral conditions.

  26. Latest ECMWF forecast is out ….
    The current run too confirms a NW movement when it approaches Sri Lanka …
    It expects LF for this system to be around Nagapattinam (app.) and expects the system to veer westwards thereafter.
    The NW movement when it approaches SL is seen at around a same time when a stronger wind field associated with the MJO is seen marked south of the system ….

  27. Last few days was overcast with showers. Today bright sun shine with low level clouds moving quite fast. Indication of rainy days ahead.

  28. how many people believe this? before 3 or 4 days of rains starting , we can see changes in Sky? it can be noticed in cloud movement & type of cloud? any one believe it ?

  29. The latest ECMWF is hinting on some organised entity ,,in S . Bay around the 1st week of December ….
    That could be of more interest …..

  30. cfs run shows current disturbance hitting central tn and moving into arb sea..and december 1st week system is expected to follow nw track from s.east bay ,crashing

  31. Classic NEM Conditions next door:
    Read the Srilankan weather forecast..So near,yet so far!
    Winds will be North-easterly and the speed will be 20-40 kmph. There may be temporary localized strong winds during thundershowers.

    Due to the active cloudiness to the West, South and East of Sri Lanka, sudden increase of wind speed over the sea areas off the coast extending from Puttalam to Trincomalee to via Galle and Pottuvil is possible.

  32. All the models predicted rain from nov 18th to 21st and then agaian on 23rd to 26th nov again they are predicting rain from 28th nov to 1st week of dec what is happening to this year NEM especially for chennai

  33. Low likely to form tomorrow.
    The upper air cyclonic circulation over south Andaman sea & adjoining southeast Bay
    of Bengal now lies over Equatorial Indian Ocean and adjoining southeast Bay of Bengal and
    extends upto 1.5 km above mean sea level. Under its influence, a low pressure area may
    form over southwest Bay of Bengal around 25th November.

    Good days ahead for us.

    • Rare sight. 1978 / 79, When I was a small kid, we were living in Shenoy nagar 4th Street close to Alwarpuram on the north banks of Vaigai river. When Vaigai was in full spate, my father took me near to the banks and we saw many houses, mostly thatched roofed houses, were engulfed by her.

  34. Nothing positive or negative from yesterday’s stand point. Condition neither improving nor deteriorating. Clouds are showing Poochandi! Current conditions and tracks should change for maximum benefit to Chennai.

  35. very early days for the 28th/29th system..but if one analyses the 850mb vorticity chart in CIMSS-you can see 2 vortices and it may eventually merge into one at a position which UKM is predicting..lets watch it unfold in the next 24hrs to get more clarity

  36. Latest GFS update is out.

    Still the forecast is consistent. Chennai will start getting rain from Thursday evening.

    @gopalll666, this is not an early days to forecast, next 5 days is reliable across the models for sure.
    That to ECMWF & GFS has predicted and they are showing consistency. Wait watch this spell is going to be massive NEM 2014.

  37. “So far I have seen…. Whenever Foreca says rains… it is happening…” – Prabhu M.K.
    Chummava Spot-on Foreca apdinu paer vechurkaanga???..thatz d reason.. πŸ™‚

  38. There is a massive circulation in S BOB currently. This is mostly going to WNW or NW close to SL and either take the path S to N across SL or skirt across SL east coast into C/S TN. However, one more circulation will be developing from the same trough near Lakshadweep and ARB. So after our vortex gives us good rains, there are chances of heavy pull effect rains from the ARB one!!

  39. I know many of you see COLA, Foreca, etc. and many other weather models for precipitation forecasts. Just because you see towers of a certain height, it doesn’t mean it is going to rain that much. I’ll brief you on what factors you have to look at these before you decide whether it is going to rain or not.
    (i) SWM
    Our beloved thunderstorm season where we have an average of close to 45 cm. However as Kea says, models basically predict rains everyday. Naturally you would look at the models and think that it would be a wet day, however it might not necessarily be one. ALWAYS analyze the conditions on your own before concluding on rains and if you aren’t able to, notice these carefully.

    If the models are showing precipitation values significantly higher than the other days, it has some significance. This is because naturally all models show rains every evening for Chennai due to the possibility of convective thunderstorms. So, if they show big towers, then it means something is spicing up and heavy rains can occur around the region, however this is also only partly true because no model is right during SWM.
    Solution : Make your own forecasts by observing or don’t arrive at a whole hearted conclusion. Analyze why the rains would/would not occur.

    (ii) NEM
    When it is NEM, the scenario is different. Models don’t show rains everyday and often show prolonged dry spells in between. This is because NEM rains are almost always triggered by systems, so models will pick up these rains and show them. Models will get the date more or less right, but amount of precipitation will never ever be correct. But overall models will be more accurate in NEM, even though amounts are never correct. Therefore if towers are shown in NEM, they carry a bit more significance than SWM towers.


  40. “Oh when I saw kea sir photo in FB i understood that he is hindi speaking guy”
    rofl..u r nicely compensating PowerPaul’s absence.. πŸ˜€
    Kea sir mein bahut acha hindi boltha hain Bijli…bachatey raho nayi soch!!! clear hain???
    Bijili…Actually, Kea speaks every Indian language very well..only that the audience will get confused whatever he speaks! πŸ˜€ lol

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