Low Pressure All Set To Form

For a couple of days Chennai has been facing cool weather despite it nearing peak summer. This kind of weather with a max temp of less than 34 degrees C will continue for the next few days.
This is because the UAC that has triggered rains in South Tamil Nadu and Sri Lanka is going to intensify and descend to lower levels, meaning an LLCC (lower level circulation center) is going to form soon. This is going to boost thunderstorm activity greatly in South and Central Tamil Nadu.

Chennai however, will have to wait. If lucky a few isolated showers might occur till 13th.


The scenario however remains unclear on WHERE the LPA is going to form. GFS indicates Arabian sea while other models indicate SW BOB. SW BOB will be much more favourable for rains for Chennai.

Chennai’s rains will depend on the location of formation of the LPA and the strength of the UAC. As of now we might get some sporadic showers, but it will be much more if SW BOB scenario takes place. This is very tricky and very tough to predict. We have to wait and see where the LLCC emerges before we can conclude on rains

Topic contributed by Sudharshan

1,692 thoughts on “Low Pressure All Set To Form

  1. Breaking news!
    NGFS also expects a cyclone near our TN coast making landfall close to Nellore.

  2. 850 mb vorticity is deepened during past 12 hrs and moved east and relocating it self!

  3. wow shear has reduced over SW bob and it reducing more! shear is increasing near WB, North bay and se Arabian sea

  4. Going to be an interesting day 🙂
    On my way to college.
    See you guys in the evening.

  5. Maddy Nice Topic. The last lines “This is very tricky and very tough to predict. We have to wait and see where the LLCC emerges before we can conclude on rains”

    Very Good!!!!

  6. The UAC at the 500 hpa level is way far west, for any LLCC to develop in the SW bay. I see only a weak surface circulation SW of Sri Lanka and it’s too close to land to develop any further.

  7. Coming GFS model, expect the change to SW Bay again. Just feeling. If they take the shear into consideration.

  8. According to unconventional theory, if MJO is at phases 5&6 and SOI stays below -10 then “UAC/system” must take N/NE track in order to survive. At present MJO within the vicinity of phase 5 & SOI touching -10. So UAC/system must travel in N/NE direction and must enter SW-BOB for its existence. It’s do or die situation for the UAC to make it to SWBOB.

  9. Guys if this system moves toarabian sea what is our chances?.
    I pray god not to go there

  10. Susa , wonderful, wonderful…. Simple n lucid language , should appeal to everyone,.Of course, guarded observations and righty so on the possible scenario to emerge…A request to you..Kea on most days contributes the daily topic. Pradeep fills in on eventful days in spite of his pressing workload..Not an easy job even if you have to pen few lines for a day’s topic.Here is where bloggers like you have to step in and reduce the burden and contribute on a regular basis. You have been one of the regular bloggers for years now and hope you would do this on a regular basis . Cheers.

  11. guys whether low/cyclone forms or not…but this condition favour us from hot weather. Still temperature not touched 100*f still now . so lets happy with this situation.

  12. The above mentioned topic has a question that whether LOW will form in Bay or Arabian Sea, good question, i would like to answer.

    It all depends on Kelvin Wave, presently it is in Phase 2, if it emerges into Phase 3, we will see the LOW in Bay otherwise GFS would be right.

    Right the forecast seems like Kelvin will emerge as a weaker system in Phase 3 and will live for short time, so chances of LOW in Bay is possible, lets keep fingers crossed.

  13. the current scenario, reminds me a famous tamil song, ” yaaraithan nambuvatho pethai nenjam”, each and every model is confusing, but i have a strong feeling that, rains for chennai is just postponed, we will definitely get our share before next monday,

  14. Courtesy: Mr. Senthil Kumar from Adambakkam

    Interestingly , the circulation moves to land , intensify near westernghats and goes to Arabian sea near mumbai.

    I foresee good rain for Tamilnadu for another 10 days. Chennai can have some showers..not expecting much

    This divergent only gives widespread rain to entire Tamilnadu

    Chennai can have heavy rains btw 16th to 18

  15. susa, simple words, easy to understand, great job, as Mr.Novak said, people like you, Vela sir, and other experts can contribute to the titles then and there. like our P.J. different views really add much needed learning experience for lay man like me, expecting more from you also susa

    • Shriram-Yes..Other bloggers should come forward and contribute the days topic..Not just few individuals..Those who keenly observe the weather patterns on a regular basis i mean…Would not like to use the often heard and used word “Analysis” Cos the word analysis(weather analysis) has a more deeper meaning which i feel in all probability should be left alone to Professionals and experts,,.I find the word “observations” is safer to use here..

  16. Super Sudharshan 🙂 simple words & easy to understand for any layman…1st 2 lines of last para sums up every thing…SW BOB is ideal spot for chennai…

  17. Weather analysis-


    Some excerpts from the File..

    Definition of Weather Analysis
    The dictionary defines “analysis” as a detailed examination of
    something. It is a process that breaks the object of the
    analysis into parts so that each part can be examined in detail.
    This process determines its nature, function, and other
    characteristics. In operational weather analysis the object is
    the atmosphere, specifically, the troposphere, where day-to-day
    weather occurs. The parts that we need to examine are the
    various weather parameters that are typically used to describe
    the atmosphere: temperature, humidity, wind speed and direction,
    atmospheric pressure, clouds, precipitation, etc. We generally
    do our analysis at one specific time in order to get a glimpse
    of what is happening in the atmosphere at that moment. However,
    analysis over time is often useful to provide a better picture
    of how things are changing.

    Atmospheric Models
    One way that a meteorologist interprets data and patterns is
    through atmospheric analysis models. An analysis model is an
    idealized representation of a weather system that helps you as a
    meteorologist visualize that system, its associated weather, and
    its evolution. It provides a distribution in space and time of
    the typical three-dimensional system structure. By comparing
    data or isopleths patterns to analysis models, you can get a
    better sense of what is happening and why. An analysis model
    gives an analyst a sense or feel for the logical distribution of
    weather parameters in both space and time.

    Those interested can go thru the link..

      • Paartha…Just happened to read this interesting link on weather analysis and how is it done..Just thought of sharing it..Also the word” Analysis” has much more deeper meaning if one goes through the link and i feel the word “observation” is relatively safer to use .

  18. Flash news!! flash news!,! as per rammb our invest has moved North east wards and now lies east of Sri Lanka and it is relocating to NE of Sri Lanka!!


  19. The upper air cyclonic circulation over southwest Bay of Bengal and adjoining Srilanka extending upto 1.5 km above mean sea level persists. Under its influence, a low pressure area would develop over southwest Bay of Bengal around 13 May.
    imd delhi morning report

  20. NAVGEM showing deep depression /cyclone crossing chennai with intense rain bands! on 15 th may

  21. El Niño in the tropical Pacific

    The tropical Pacific is in the early stages of El Niño. Based upon model outlooks and current observations, the Bureau’s ENSO Tracker has been raised to El Niño status.

    El Niño–Southern Oscillation (ENSO) indicators have shown a steady trend towards El Niño levels since the start of the year. Sea surface temperatures in the tropical Pacific Ocean have exceeded El Niño thresholds for the past month, supported by warmer-than-average waters below the surface. Trade winds have remained consistently weaker than average since the start of the year, cloudiness at the Date Line has increased and the Southern Oscillation Index (SOI) has remained negative for several months. These indicators suggest the tropical Pacific Ocean and atmosphere have started to couple and reinforce each other, indicating El Niño is likely to persist in the coming months.

    International climate models surveyed by the Bureau indicate that tropical Pacific Ocean temperatures are likely to remain above El Niño thresholds through the coming southern winter and at least into spring.

    El Niño is often associated with below-average winter and spring rainfall over eastern Australia, and above-average daytime temperatures over the southern half of the country. However, the current May to July outlook suggests much of Australia is likely to be wetter than average. This is because a warmer-than-average Indian Ocean is dominating this outlook. El Niño is expected to become the dominant influence on Australian climate during the second half of the year.

  22. The steering wind pattern forecast by GFS itself is a mistake and a big error.
    When ITCZ is strengthening near Equator, the lower level steering winds must be from SW to NE from Comorin to South Bay areas and in Arabian Sea it must be scattered due to HPA over Central Arabian Sea, hence the lower level steering will not even enter Arabian Sea, this wind will come from NW Indian Ocean and move towards ENE direction across Comorin and to South Bay.

    This lower level steering winds will take the LOW towards SW Bay of Bengal since Kelvin Wave is moving towards Phase 3 in next 2 days. So GFS is blabbering.

    GFS is expected to come in line with ECMWF.

    Since the confusions are going on, i would like to summarize that the present LOW in GOM will move up NE and will emerge as a strong LOW over North Coastal TN by 14th as Kelvin Wave likely in Phase 3 by 14th. This movement will give good rainfall over NTN and Chennai from 13th overnight or 14th early morning.

    This LOW has a chance to become a Depression, but it is a remote chance and i do not want to rule out, but a strong LOW or WML over North Coastal TN by 14th is possible as per ECMWF.

  23. SST is highly favorable, only if VWS don’t disturb the LAP, it sure to become a significant cyclone.

  24. The latest ENSO Wrap-Up (Link: “http://e.bom.gov.au/link/id/zzzz555189a41b646393Pzzzz53a951a58ea2c418/page.html”)

    ENSO Tracker (Link: “http://e.bom.gov.au/link/id/zzzz555189a41ba79072Pzzzz53a951a58ea2c418/page.html”)

    and Climate Model Summary (Link: “http://e.bom.gov.au/link/id/zzzz555189a41beea565Pzzzz53a951a58ea2c418/page.html”)

    are now available on the Bureau’s website.

  25. Manamelkudi (Pudukkottai Dist)


    Sivakasi (Virudhunagar Dist)


    Coonoor (Nilgiris Dist), Pamban (Ramanathapuram Dist), Sankaridurg (Salem Dist)

    4 each

    Coonoor pto (Nilgiris Dist), Kadaladi (Ramanathapuram Dist), Kamudhi arg (Ramanathapuram Dist), Kamudhi (Ramanathapuram Dist), Mudukulatur (Ramanathapuram Dist)

    3 each

  26. Thats very positive ENSO update from Australian Met.

    ELNINO tracker alert has reached the maximum level.

    NINO 3 is at the peak with 1.2C above normal, 0.2C increased in the past 2 weeks.
    NINO 3.4 remains samd with 1.0C above normal and NINO 4 has reduced 0.1C since last 2 weeks time.
    NINO 3 and 3.4 is hotter than NINO 4.
    SOI fell below -8.0 (ELNINO Threshold) and as per the following link, it is -9.9.
    Trade winds are consistently weaker and Cloudiness near date line has increased and it is consistent.
    Positive IOD likely by June.

    The above conditions indicates that perfect ELNINO conditions has arrived.


    • Salem will get sure shot rains in coming days. Bangalore will mostly be dry for next 3 days.

    • Nothing much for Bangalore I believe. When Chennai itself is struggling to post numbers on this one, how come Bangalore!! Expect nothing more than a 1cm

      • Yeah, that’s on the cards. Expecting a cool weekend of 22C Max. If the system moves NW into interior TN, then deluge is on the cards for Bengaluru. But that’s not the scenario now. The Low expected to Skirt along TN coast.

Please restrict Comments to Weather only

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s