TN to stay dry

Two synoptic disturbances at two different ends persist & remain weak. The Low Pressure Area (LPA) over extreme North-NW India is seen interacting with a trough associated with a western disturbance which will bring heavy rainfall to parts of J&K, Punjab, and HP. Another LPA over Bihar is seen pulling moist winds from the Bay and creating a short sheet of rain wave along Bihar, Gangetic WB and foothills of Himalayas along the Northeastern states.

02. India_Sat

Chennai – Expect clear skies in the morning, turning partly cloudy as the day progresses. Max temp to remain around 34-35c

Coimbatore – Likely to remain warm with max temp nearing 32-33c

Madurai – Another hot day with temp of 38c with slight chance of showers in one or two places.

Vellore – Temp will be around 33-34c

Trichy – Likely to see another uneasy day with temp 37-38c

908 thoughts on “TN to stay dry

  1. Rains hav ceased over majority of india except for pockets in n and ne Amritsar 91, Jamshedpur 58 mm, hvy rains over pats of nw pak

    • Hope Beas is getting good rains. The river is the major source for irrigation and drinking water . It caters to a wide area over there.

  2. North-East monsoon

    Meanwhile, the Northwest Pacific and progressively the South China Sea (lying next to the Bay) could see winds reverse turn from the weekend and blow north-easterly.

    This should herald the northeast monsoon over these parts even as a helpful anti-cyclonic circulation forms over North Bay of Bengal.

    Southern parts of the Bay may get ready to receive north-easterly flows from the first week of October and gradually the North-East monsoon.

    October 15-20 is the normal timeline for the arrival of North-East monsoon (monsoon in reverse or winter monsoon) for the Bay and peninsular India.

    (This article was published on September 22, 2015)

  3. Let us recall few weather terms:

    Cyclonic Circulation (Cycir)

    Atmospheric wind flow in upper levels associated with any low pressure system. The wind flow is counter clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

    Anticyclonic circulation

    Atmospheric wind flow in upper levels associated with any high pressure system. The wind flow is clockwise in the Northern Hemisphere and counter clockwise in the Southern Hemisphere.

    Low pressure Area (LOPAR)/ well marked LOPAR

    Area in the atmosphere in which the pressures are lower than those of the surrounding region at the same level and is represented on a synoptic chart by a system of one closed isobar (wind speed on the surface < 17 Knots (Kts) when the system is at sea or one closed isobar in the radius of 3 Deg. from the centre over land).


    Intense low pressure system represented on a synoptic chart by two or three closed isobars at 2 hPa interval and wind speed from 17 to 27 Kts at sea and two closed isobars in the radius of 3 Deg. from the centre over land.

    Deep Depression

    Intense low pressure system represented on a synoptic chart by two or three closed isobars at 2 hPa interval and wind speed from 28 to 33 Kts at sea and three to four closed isobars in the radius of 3 Deg. from the centre over land.

    Cyclonic Storm

    Intense low pressure system represented on a synoptic chart by more than four closed isobars at 2 hPa interval and in which the wind speed on surface level is in between 34 – 47 Kts.

    Severe Cyclonic Strom

    Intense low pressure system represented on a synoptic chart by more than four closed isobars at 2 hPa interval and in which the wind speed on surface level is in between 48 – 63 Kts.

    Very Severe Cyclonic Storm

    Intense low pressure system represented on a synoptic chart by more than four closed isobars at 2 hPa interval and in which the wind speed on surface level is in between 64 – 119 Kts.

    Super cyclonic storm

    Intense low pressure system represented on a synoptic chart by more than four closed isobars at 2 hPa interval and in which the wind speed on surface level is 120 Kts. and above.

    Western Disturbance

    Weather disturbances noticed as cyclonic circulation/trough in the mid and lower tropospheric levels or as a low pressure area on the surface, which occur in middle latitude westerlies and originate over the Mediterranean Sea, Caspian Sea and Black Sea and move eastwards across north India.

    Western Depression

    Weather system, which originate over the Mediterranean Sea, Caspian Sea and Black Sea and approach northwest India and is defined by two or more closed isobars on the surface.

    Induced low

    Under the influence of the western disturbance, sometimes a low is developed to the south of the system called as induced low.

    Induced cyclonic circulation

    Under the influence of the western disturbance, sometimes a cyclonic circulation is developed to the south of the system called as induced cyclonic circulation.


    A line or curve along which the atmospheric pressure is minimum. Pressure increases on both sides of the line or curve.

    Trough in westerlies

    A moving wave perturbation in mid latitude regions which are present throughout the year which move from west to east and entire globe. These systems generally affect the northern parts of India.

    Trough in easterlies

    A moving wave perturbation in the equatorial easterly wave, moving from east to west.

    Easterly Waves

    A shallow trough disturbance in the easterly current of the tropics, more in evidence in the upper level winds than in surface pressure, whose passage westwards is followed by a marked intensification of cloudy, showery weather. The southern peninsular region is affected by easterly waves.

    Shear line

    A line or narrow zone across which there is an abrupt change in the horizontal wind component; a line of maximum horizontal wind shear.


    An elongated area of relatively high atmospheric pressure almost always associated with and most clearly identified as an area of maximum anticyclonic curvature of wind flow.


    A line across which there is an abrupt change in wind direction


    An atmospheric layer in which all significant weather phenomena occur. The troposphere is characterized by decreasing temperature with height. It is the lowest layer of atmosphere, which may extend upto8km near poles and 18 km near equator.

    Lower troposphere level

    Part of the troposphere upto 2.1 km above mean Sea level (a.s.l)

    Mid troposphere level

    Part of the troposphere from 2.1 km a.s.l. but below 7.6 km a.s.l

    Upper troposphere level

    Part of the troposphere from 7.6 km a.s.l to a height upto which temperature decreases with height.

  4. @bhaskaran19:disqus

    Great opening for me for the day. Great news on NE Monsoon. However I was saying this for the past few weeks that NE Monsoon will set in early this time, meant that during 2nd week of October.

    So double happy.

    • Yes I read your postings -I knew that there will be certainly a note from you on this. But my gut feeling is unlike last year (NEM started on 17th Oct) this year could be couple of days in advance.

  5. As usual for NE-curved WP-typhoons, models started confusing. GFS is somewhat better when compared to ECMWF in foreseeing the future track of Dujuan.

    Dujuan’s track based on 2D-map model:
    It looks Dujuan will be encountering mid-latitude upper-level trough (indicated as yellow lines) after it comes close to E/NE of Taiwan. Due to this interaction Dujuan will take very sharp E/NE track, which will brush off entire Japan. This 2D-gyric map model track (indicated in white line) is in good agreement with GFS track.

    Unfortunately ECMWF, JTWS, CIMSS will miss their forecast very badly. GFS may emerge as sole winner.Time will reveal the real track.

    Dujuan’s 2D-gyric map model:

  6. North-West India and adjoining East may start drying up as the flows turn dry westerly guided by a typhoon building in the Pacific.
    This typhoon will materialise from a weather disturbance already located over the open waters of south of Japan.
    Flows headed for the typhoon and across the Bay of Bengal may rebound off the Arakan Valley in Myanmar and lob in a low-pressure area over East Bay of Bengal.
    This ‘low’ is forecast to cross the Odisha-Andhra Pradesh coast during the last few days of the month and propel another wet spell into Central India. It could delay the resumption of withdrawal of monsoon from south of the Vindhyas.

      • i have already read that, and i hv already liked it also, infact i go thro every comments when i enter here, in the same article this piece of information was given, how many people go thro the entire article?, most view the comment posted here only,

      • i posted the above information to remind that swm may not fully withdrawn from entire country before this month end only,

  7. Equatorial SOI value in August was -2.20. The same pattern was followed in other ELNINO years like 1972, 1982, 1987, 1997 and 2002. We had good NEM other than 1982. The year 1982 had weak SST anomaly even though it was said as Positive IOD year. Years like 1987, 1997, 2002 & 2009 had strong Positive SST Anomaly and it was perfectly matching with Positive IOD.

    In Aug 1997 -2.3
    Aug 1987 -1.4
    Aug 1972 -1.5

    Hence good NEM on the cards.

  8. Understanding the monsoon
    The surface waters of the north Bay of Bengal are among the freshest (i.e. least saline) anywhere in the world, due to monsoon rains and the discharge of fresh water from several mighty rivers. The warm, fresh upper layer of the Bay supplies prodigious amounts of moisture and heat to the atmosphere, forming masses of tall, dark clouds that bring monsoon rain deep inland.
    The upper ocean interacts with the atmosphere. Monsoon winds and ocean currents stir the fresh water over large distances, and 200-kilometer wide ocean eddies draw it into thin filaments. Yet the mixing between river water and sea water is very slow. The thin, fresh layer responds quickly to changes on the surface caused by winds and sunlight. At the same time, it helps to trap some of the sun’s heat at subsurface depths, to be released into the atmosphere days and weeks later.

  9. Metro Water has identified 30 water bodies in Chennai Metropolitan Area (CMA) to assess their potential for ground water.Currently, the water level in all the four reservoirs is 365 million cubic feet, which is way low when compared to 2,338 million cubic feet of water available during this period last year.
    “We are currently tapping 250 agricultural wells and plans are on to tap 80 more wells to provide adequate supply to the city, including the added areas,” said the official.
    The meteorology department officials have informed us that the monsoon this year would be normal. We are now pinning our hopes on it,” the official said.

  10. It’s very normal to see cyclone targeting AP/orissa during tis time.. hope cyclone brings in easterly pulse and activates nem by Oct 2nd week

  11. Early onset of NEM cannot be ruled out. The second week of October is the time NEM to set in. Weak MJO likely to emerge in Phase 2 by 07th or 08th will trigger this monsoon.

    The point is, it may start with weak rainfall activity. Then we might have some dry spells for at least 10-15 days time. Positive real time OLR likely to dominate those dry spell days. After 22nd of October once again NEM will strengthen and can expect heavy rainfall, MJO in Phase 2 likely to strengthen from 21st October and move to Phase 3, also a strong system possible to form. Kelvin also strengthens in Phase 3 by mid of October, so this is the time that Positive IOD might start to weaken.

    My guess is that NEM might begin between 10th to 13th.

  12. come on..there is no strong relation between these pre-nem system and elnino… transition period produce monsters in both elnino,lanina regimes.

  13. Hope System makes landfall during 10 and 11 near kakinada range
    I could go to Annavaram temples during those days near vizag

  14. Next week system is well likely to fall under southern quadrant of upper troposphere ridge and so it is more likely to follow w-nw track with more weightage to westerly genesis position is very crucial and tat more likely to decide the landfall point..Last night GEM run was expecting the system genesis over east central bay and making the system to make LF over vizag with mean westerly track!! ecmwf expecting it over north Andaman sea with westerly track where as gfs over s.andaman sea with w-nw-w track..

  15. OLR on Oct 08th 2005 and OLR on Oct 11th 2005.
    MJO was in Phase 2, ER Wave Negative and Kelvin too in Phase 2. Full action packed season.

    MJO strong negative OLR over TN alone. Then ER strong negative OLR over TN.
    What else required. Perfect Conditions. Unfortunate that I was not observing all these through Kea Blog
    or Weather Charts that time.

    Can anyone bring the cloud activity of that day. Since MJO and ER was in full action, on 11th October we got massive rainfall from afternoon to evening.

      • Yes, my relatives came from Bangalore after 11th and said about that, when i said about 11th rain, they said like this. Rain is always less in Chennai, you people come to Bangalore. I was angry after listening to that, but was silent and wanted the nature to reply at that moment. Then what happened everyone knows.

        The same relative came in December end and said that you people had extraordinary rainfall this time. I never thought this would happen.

      • Most of the times people speak without knowing statistics. ..bang annual rain is much less than chennai. .. just that it drizzles more in bang n chennai had more Warmer days n non rainy days there is Always the wrong illusion

  16. with just one month to go for the starting of this yr season, this is the condition of Vedanthankal lake, now, with less rainfall, as well as the water ways to the lake also enchroched, the lake is almost dry , will the coming nem rains help the winged visitors from various countries to have their stay this year also, and in turn which helps the farming in those areas?

    • Almost dried..nothing in that..even our lakes are also fully dry..we need badly a excess nem this should and will happen..

  17. Before the monster forms in andaman, a trough over North TN will give rains on sat/sun…After that, it will be in hands of the system..GFS hints that ..

  18. Rainfall update today

    Pochampalli (Krishnagiri Dist) – 6

    Tirupattur (Vellore Dist), Penucondapuram (Krishnagiri Dist), Yercaud (Salem Dist) – 5 each

    Tirupathur pto (Vellore Dist), Uthangarai (Krishnagiri Dist) – 4 each

  19. Unexpected heavy rains in TN ending 8:30 am on 23rd Sept.
    Tirupathur AGRO – 99
    Jolarpet AGRO – 74
    Kalrayan Hills – 58
    Natrampalli – 56
    Bargur – 54
    Kandhili – 53
    Yercaud – 50
    Erumaipatti – 45
    Tirupathur IMD – 44
    Veppanapalli – 42
    Ayodhiyapttinam – 21
    Peddanaickenpalayam – 21
    Usilampatti AGRO – 18
    Salem – 16
    Attur – 15

  20. Mouli I have a radar image of strong thunderstorms weakening over Salem and new blobs developing over Krishnagiri and Tirupathur areas. But don’t have the image of those storms at peak strength. Here are the images

  21. NAO likely to be neutral from 01st October to first week of November. Then turning Negative by November 10th.

    Neutral in September, then turning Negative during NEM season is good for NEM. It happened in the past.

  22. @kriKrishna_Nanganallur tis is the basics of steering as most systems follow this pattern forced by an external force called high pressure area over a tropical cyclonic system.. some strong system hav its movement through both internal and external forces.. here the axis of hpa is marked as “H” and extending flow from hpa is called as ridge. it revolve around the axis in clockwise flow. so the storm moves around it.(first pic)..second pic is the typical november environment where the intensity of the system adn hpa decides the movement .. it si also a complex environment(second pic).. third pic is the early oct environment .. apart from this westerly moving trough in mid latitude alters the position of ridge and influence the track of the system.. weak system gets steered by low -mid level flow and strong one will be mostly upper-mid level flow

  23. Just returned from outside – mercury certainly shot up after two days of lull, unlike yesterday where the sky was clear today it is totally different, humid as well

  24. I forgot to say this.. most of the system gets influenced by the ridge that is seen right of the system. So in most cases our nem system gets steered by the ridge tat is extending from west pacific..

  25. From today Mid Level wind over North Coastal TN will change to Easterly, some times Northerly also. This trend will continue until month end. Till 26th no chance for rainfall over North Coastal TN, especially Chennai.

    We have a chance on 28th.

  26. There is a possibility of minimal alteration of ridge on 30th sep and so the system may b moving west in last 36 hrs before making lf.

  27. Btw, had a discussion with my co passenger , a native of Vishaka.. He seems to have fair knowledge of weather, like us..Obviously, after discussing other topics. I turned my attention towards 12/10/2014..
    Asked him to narrate his experience briefly..
    He said, why are you reminding that horrifying experience again…Basically I’m a strong hearted person. But that 7 hours from 8am till 2pm was the most terrifying part of my life. First time I have felt bow nature can dictate terms to humanity. The howling sounds since midnight of 11th were music to my ears of different kind…My daughter was literally crying non stop, seeing the window panes getting shattered with huge noise. He specifically talked about the time when the Eye wall cross over was in effect and howw things were calm n quite for a while.
    He said ” Sir, the second part was worst than the first. Winds started reversing and the force was just unexplainable..It took at Least 3 days for the nerves to calm down.. He concluded.

  28. Global surface temperature in relation to Northeast monsoon rainfall.

    The association between the global surface air temperature anomalies and
    NEMR is examined in the present study. NEMR is more variable in the coastal districts compared to interior districts. Surface air temperature is one of the
    factors that influence monsoon variability. The distribution of surface air temperature over land and sea determines the locations of heat source and
    sink which in turn affect circulation patterns through thermal and latent heat
    energy exchange between atmosphere and the surface beneath. NEM period
    of 1968 showed that it is related to large scale anomalies in the upper level
    flow pattern in the middle and higher latitudes.

    STA during Successful NEM Years:
    it is observed that during the month of September, the CCs over regions of
    northern Africa around 15◦N to 20◦N latitude are positive while CCs over Eurasian region around 50◦N to 60◦N latitude are negative. This means
    that above (below) normal NEMR years are associated with increased (decreased) south–north temperature gradient in the month of September
    from subtropics (high latitudes) to higher latitudes (subtropics) over the longitudinal belt (0–40◦E). Also significant positive CCs are observed over
    the central and eastern equatorial Pacific and significant negative CCs are observed over the western Pacific region.

  29. Rao,

    Did you noticed that following study. They strongly say that West Pacific Negative STA anomaly increases the chances of above normal NEM. I said this few months back. This creates more ACC over West Pacific and over Myanmar or Thailand region. This pushes the moisture with full strength towards Bay. This influences the rainfall pattern over TN from October to December.

    • Yes Partha, this phenomenon I used to watch for years even when I doesn’t know about SSTA or Nino concepts. I used to watch IMD-OLR maps might be since 2001 onwards due to availability of good speed internet. Whenever there is strong +ve OLR over South China Sea/ surrounding areas, our monsoons becomes more vigorous and vice-versa.

      • Yes, Negative NAO throws Colder winds across Europe and Siberia, this also created higher HPA and this inturn helps the lower latitude to gain some moisture. This time Wheelor and Hendon models shows that Negative NAO likely from November 1st week, till then NAO will be negatively neutral, this is why some models are indicating that Below Normal Rainfall during October.

  30. Short comparison of 2005 and 2013 lower level and upper level conditions.Being a negative iod year, 2013 shld hav been one remarkable year like 2005.but somehow it missed very badly.. i hav attached 4 images showing 2005 (lower&Upper level conditions) and 2013 conditions respectively .
    2005 lower and upper level streamfunction followed by 2013.

  31. I strongly believe that the following sequence (MJO>SOI>IOD>QBO) will have greater influence on major aspects of a synoptic system especially in genesis, track, intensity, etc. It looks the forecasted Chapala will be having more W/NW track like hudhud due to movement of MJO in the order of 5/6 towards 7/8 similar to hudhud. Where as for Phailin-2013, MJO completely stayed at phase 6, which might have exhibited NW-track due to proper alignment of ridge position.

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