Trough at lower level triggers rains across Peninsula

A Feeble trough at lower level, seen extending from Central India into Lakshadweep through Karnataka along with another trough from NE India into West Central Bay of Bengal caused much needed thundershowers along most parts of Karnataka, Kerala, Rayalaseema, and Telangana & AP. An upper air cyclonic circulation in West Central Bay along with the above mentioned synoptics would enhance the probability of rains for Peninsular India and adjoining East coast. This scenario will continue for the next few days which would make monsoon active over Southern states except TN which falls under rain shadow region.

However Parts of North & Central Tamilnadu coast including Cuddalore, Villupuram and North TN regions including Vellore, Tiruvannamalai, Chennai, Tiruvallur, and Kanchipuram could see evening thunderstorms.

Chennai – Partly cloudy and Pleasant day expected. Temp is more likely stay below 34c. Evening thundershowers expected in the city and suburbs.

Coimbatore – Partly cloudy conditions with slight possibility of showers/drizzles. Max temp of 32c.

Madurai – Warm & partly cloudy day expected with max temp at 36c.

880 thoughts on “Trough at lower level triggers rains across Peninsula

  1. Gud morning blogers yesterday my area does not even recives drizzles but i expected more than that.i dont know what nature has in store for us today.:(.lets wait and watch.

  2. Temperature would be around 32-33 degree . Ts activity increases towards afternoon in interiors , and storms could move towards entire parts of Chennai .

  3. The forecast these days are not that worse.The temperatures have remained below normal as per forecasts, and indeed pockets of suburbs have received rains as well. Models are not to be blamed completely. With the resolution they take and the grid they select, the data put in does predict the future conditions well on some occasions. Better forecasts will be available in the days to come.

      • Yeah, exactly, the window kept open for is about 12 hours during which there can be some accumulated rains in and around the region they select.

    • And of course as it should be, a clear wrap up of winds and rains about the center. Perfect September synoptic LOW, with vertical wind shear and other conditions coming in line to the transition period.

      • Seems the 3 models vary in their upper level analysis significantly, although they are in line with the overall strength, position and intensity of the upper Tropospheric ridge. The system’s intensity is still uncertain. CMC as usual , take it as casual to an intense system.

  4. Roger Federer just finished John Isner in style. With Murray and Berdych gone the draw gets murkier. Stan the Man and Novak should be the main hurdle. 7-0 in the first set tie breaker icing on the cake.

  5. This year’s early withdrawal of the southwest monsoon from western India could lead to an early onset of the northeast monsoon over southern states. Spread over October till December, this retreating monsoon brings rainfall over Karnataka, Kerala, Tamil Nadu and Andhra Pradesh.
    “Due to El Nino, we expect (southwest monsoon’s) withdrawal from central India including Gujarat, Madhya Pradesh and Maharashtra by September 15-20, rather than October 1. The wind directions are simultaneously going to change to north-easterly, leading to the onset (of northeast monsoon),” said a scientist from Indian Institute of Tropical Meteorology in Pune.
    “By September 9, we will come up with our next outlook on weather for next 20 days. ,” the scientist said.
    The IMD will issue its forecast by end-September, said DS Pai, head of long-range forecast at IMD.
    Read more at:

  6. The Indian Meteorological Department has not downgraded its June-September monsoon forecast from the 88 percent of long-period average (LPA) it had put out recently, its Director DS Pai told CNBC-TV18.
    “We are not revising our forecast of 88 percentage of LPA, plus or minus 4 percent. That still holds intact,” Pai told CNBC-TV18. He added that while monsoons were near normal in the east and north east, north west was amongst the hit, at 14 percent, with sub-regions like Punjab and Haryana witnessing a deficit about 30-40 percent.
    Read more at:

  7. The early withdrawal was said in July itself in Kea Blog. If i remember it was said by Mr, Guest11K. Many of us too expected it to happen. Hence there is no difference in ELNINO year, nature playing its role as per the phenomenon’s.

    Now Positive IOD giving good rainfall across peninsula, hope there is not much effect on Tamil Nadu, i too want rain, cannot bare the heat until NEM.

  8. i feel that cannot happen, when SWM withdrawal have begun, wind will change drastically from now on over north to central india. Also forecast that central india withdrawal to begin by mid of the month, hence this lpa will be ruled out from central india in the upcoming days.

  9. Bay is not going to produce any strong systems this September. There is no support from atmospheric and oceanic waves this month to trigger such strong systems. Day by day the steering winds are losing its direction and strength. There are some hopes remain for south india to get rainfall for next 20 days.

    Another observation from my side is the last week of September will be left completely dry across the country.

    The atmospheric rossby likely to bring some cheers to Chennai on 11th, 12th and then from 15th to 17th. These days we are likely to see some Thunderstorms.

    NEM likely to begin on or before 15th October. A D or DD likely by 15th over SW bay and move towards TN-AP coast. Positive end to October and Excess November to begin. We have good NEM on the cards this time, lets not worry about September, lets be happy with NEM 2015. Cheers…

  10. OMG….By going shris featured comment …nem onset ll be in october first week itself ….they are indicating withdrawal from maharastra on sep 20 which is very early….

  11. If u could remember SWM in 2013, when it was withdrawing from east India, it was Cyclone Phailin that put a halt on Monsoon withdrawal for another week or so. This is something normal on most occasions. But withdrawal line after that could accelerate down. So, withdrawal line getting started, does not guarantee Monsoon rains may die out in the immediate.

    • Agree with you GTS, but taking ELNINO into consideration, this should downgrade the rainfall across north and central india by mid of this month, normally we have seen that withdrawal picks by first week of September over NW India, but to draw the second line it may even take 20 days more, but this is during normal years. Since it is ELNINO year, i am sure that LOW over Central India can be ruled out.

      • Nothing can be said 100% Partha. Because , even the researchers always say all El Nino events aren’t the same. Dynamics do get included and added to the climatological mean. So anything can happen is my opinion.As , u say it may even weaken without reaching central or adjoining west India. It is better if we wait and watch.

      • Just compared Atmospheric Circulations for the past and now. It is almost similar when comparing with same years which had same strength of ELNINO. Only thing to say is that SWM is below normal this time, hence no change except 1997 which had Positive IOD.

        In 1982, -15.5%
        In 1987, -19.7%
        In 1991, -9.5%
        In 2002, -15% across the country
        In 2009 – -24%

  12. Good news is that 2015 NEM onset might be taking place with good system (DD/a cyclone) originating from SC/SW BOB between October 10 & 15, which will cross at NTN/SAP near Chennai. This system will mimic 1972/1982 Chennai targeted October cyclones.

  13. Have interesting posting our blogger, astronomer and my friend Dhinakar Rajaram in Face Book Just now recollecting on this day 8th September 2012 heavy down pour and wanting to know whether history will repeat.

  14. Will this swm can able to see like this?
    swm rainfall over chennai in last decades
    2015-330mm till sep8 still 22 days left….

  15. Gokul (TBM) next sub tropical low in westerlies over s.ind ocean extending upto 25s after sep 11th which is coinciding with active monsoon condition in our basin along with a offshore trough in w.coast and lpa in bay.. try to check that entire run

  16. An El Nino has very different effects on the south-west and north-east monsoons. This abnormal warming of the equatorial waters of the central and eastern Pacific has often been associated with failure of the south-west monsoon. But the very same phenomenon appears to have just
    the opposite effect on the north-east monsoon, leading to more bountiful rain.

  17. The latest ECMWF update is out, and in this one, the system is expected to cross somewhere close to n.ap- south odisha coast, and takes it inland in a more wnw direction traversing through n.coastal AP , Chhattisgarh Telangana border , interior Maharashtra until sw MP and adjoining Gujarat. Consensus improving.

  18. The remnant of WP system close to MTC triggering the system over East Central Bay on 14th. This is likely to streamline the CEW back to track over Bay of Bengal. The clockwise circulating gyre will be back to its position over just south of Equatorial IO at adjoining Central IO at around 75 to 80E. These conditions are favouring the upcoming system over Bay.

  19. changing pictures of IMD – gfs day by day i dont thing anything fruitful will happen to chennai this september lol at this models and forecasts

  20. Heavy rains likely in Raichur Kurnool Bellary Dharward koppal Gadag Bidar North Anantapur Kalaburigi by evening
    Sunkesula inflow 19000 cusecs
    Tungabhadra dam inflow likely to increase soon

  21. Seriously It has been a very bad one month or so !! We are talking only imaginative things…why can’t we conentrate what needs to be done !! we can have those fruitful discussion. However, let me not forget to thank people who are extensively involved in bring up the facts

    • Guess those increased SST anomalies may be more attributed to the current suppressed phase of MJO over Indian Ocean. Even the forecasts had expected a 0.25 to 0.5 degree rise in SSTA across western Indian Ocean in response to MJO and the associated easterly wind anomalies. So, this might settle down again back to low DMI values once the situation moves away.Not sufficient enough to declare an event on temporal scale in association to these temporary stress forcings.

    • Interesting thing is that SSTA at Peru/Chile coast started warming. It’s good for speeding elnino dynamics to be aligned with atmosphere in 100% manner.

  22. Seems the latest Monsoon withdrawal line was drawn with much caution. With models beginning to pick a LOW, the line is just extending slowly eastwards, but not below latitude 25 N.

  23. Oh no…when will experts takes rest… Too much technical discussion keeping me away from blog from11am…konjam freeya vidunga pa

  24. Normal monsoonal winds are forecasted by models, this is the indication of IOD value coming down in the near future.

    Usually during Positive IOD event, the wind at Equator will be Easterly, this will stop the free flow of Cross Equatorial Wind towards Bay of Bengal. This will suppress the monsoonal winds across the bay, hence the moisture will come down. However the forecast suggests that CEW will be back into action from 13th onwards, the CEW likely to be back across EQ IO and system likely to form over Bay and increase in the moisture to happen, this indicates that Positive IOD will weaken in the coming weeks.

  25. Massive Rains in Kerala

    Kannur district
    Kannur – 109 mm
    Taliparamba – 107 mm
    Thalassery – 97 mm
    Cheruthazham – 96 mm

    Kozhikode district
    Kuttiyadi – 108 mm
    Kozhikode – 89 mm
    Quilandy – 94 mm

    Wayanad district
    Vyttiri – 143 mm

  26. Myanmar Weather Forecast on SWM Withdrawal, something to cheer about. I have never seen this type of forecast in IMD. See their forecast of Withdrawal. Their September forecast:

    Southwest monsoon is likely to withdrawal in:

    Northern Myanmar Areas during (11-16) of September
    Central Myanmar Areas during (17-22) of September
    Deltaic Areas during (23-27) of September
    The Whole country during 28th September to 3rd October

    Bay of Bengal Condition

    Out of (4) Low Pressure Areas, (2) may further intensify into the Depression in the Bay of Bengal. Monsoon is likely weak to moderate in the Andaman Sea and Bay of Bengal.

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