NEM 2014 Summary - To sum up Systems form October till November 20th (projected)

1. Cyclone Hudhud (10 to 14th October) - Perfect Cyclone made a landfall, close as a super cyclone.
As per IMD, the 1999 Orissa cyclone is the strongest storm to hit the Indian coast since 1891 with a wind speed of nearly 260 kmph and the  the second strongest storm was Phailin which hit Gopalpur in Odisha at a wind speed of 220 kmph. IMD says Hudhud is the 3rd most strongest Cyclone to make landfall since 1891 at a wind speed of 206km/hrhttp://timesofindia.indiatimes.com/city/visakhapatnam/Vizag-first-Indian-city-directly-hit-by-cyclone-Hudhud/articleshow/44864271.cms These are some of the IMD officials who are spoiling the name of IMD without knowing facts. The 1964 Dhanushkodi cyclone, 1990 Andhra Cyclone,  1977 Andhra Cyclone, Tyhoon Gay 1989 (Andhra) all made landfall with over 220 km/hr winds. All were Super Cyclones.  Tamil Nadu did not get any rains from Hudhud.

Coming to Hudhud with over 200 km/hr winds and rainfall of 500 mm was reported in some places in AP in two days. Orissa too got blinding rains of over 400 mm at some places in 2 days.  Places in Madhya Pradesh too reported 300 mm in a day. The rains were right upto Uttar Padesh. Nepal got surprise hit and caused Avalanches.


2.NEM onset and Comrin-Mannar-Sri lanka Circulation (16-24th October) - stood like a wall
Long lasting system like the WML in Andhra Pradesh in 2013. It stood like a wall and gave continous rains. The places in Tirunelveli / Tuticorin got over 500 mm rains. Right from Kanyakumari to Chennai got widespread rains. Chennai got some 300 mm rains from this system. The dry regions of Thoothukudi and Tirunelvei cannot be called as drought hit regions anymore.

3. Cyclone Nilofer - (25-30th October) - landfall was never there
It intensified in open waters, when it was close to Indian Coast as a Depression. The wind discontinuity gave Coimbatore, Theni, Kanyakumari, Madurai, trichy, Nilgiris and Tuticorin all got good rains. Some places in Trichy close to 200 mm in a day. The cyclone excited many weather freaks like us in Chennai, from Mumbai, Gujarat and also Pakistan. But the end was written before. It went into very very high VWS and got sliced off. Oman got more rains than Pakistan and Gujarat.

4.Tamil Nadu Circulation (November 1st to 4th) - Gave moderate rains
SW bay Circulation persisted close to TN and gave good rains for a day or two to Chennai. Madurai got 150 mm from this system. Many other places from Kanyakumari, Theni, Tirunelveli too got 100-150 rainfall.

5.Deep Depression (November 4th- till date) - Wrapped by Dry Air and cut-off by Vertical Wind shear  
The elonagted trough from north TN to Andaman created this Depression. It caught all models off track, they showed Burma, Bangaldesh, Odisha, West Bengal and North AP. Wrapped by Dry Air and cut-off by Vertical Wind shear, the end was known to everyone. The system will come to TN coast as a very weak low. Some places in South AP may get around 40-60 mm rainfall from this system. North TN including Chennai will also get light rains on 9/10th.

6. Next System (November 12th to 15th) - Has to cross Major hurdle of VWS  
The system was expected for TN crash as a significant cyclone but all models have scaled it down. It has to pass major hurdle of high Wind shear. It seems we wont get Ashoba cyclone very easily. Even it weakens. It will give good rains to Chennai and TN as it will be rain filled system. Rains can be expected from 12th November.

7. Future Low (November 21st expected )

Too early to speak. But if it forms it will affect TN and Sri Lanka

North East Monsoon 2013 - End of Season Summary

Background

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The 2013 NEM was unique, there was not even a single Easterly Wave which affected TN. All the easterly waves either intensified into Depression or Cyclones in their early stages itself. TN missed most of the systems and so the rains missed us resulting in 2nd consecutive NEM failure for TN. The Two Depression which crossed TN gave rains for only for 1 day.

1st system - Very Severe Cyclone Phailin (Most Powerful)

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The 1st system to form in October was Cyclone Phailin (October 8 to 15) it nearly intensified into Super Cyclone. It went to Orissa/North AP. Tamil Nadu did not get any rainfall from it. Many places in Orissa got close to 500 mm. Technically NEM set in after this Cyclone. The Cyclone killed around 44 people in Orissa. The cyclone 1st made landfall in Mayabunder in Andaman Islands where it pounded 750 mm rainfall in just 3 days.

2nd System - WML in Andhra Pradesh (Dumped record rains and stood like a Rock)

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The second one was a Well Marked Low Pressure Area (WML) (October 20-28). It formed near TN and moved north to AP. This system gave rains to Tamil Nadu for a day or 2. It nearly intensified into a Depression and was a record WML as it lasted around 8-9 days. Andhra got mammoth rains. Kallingapattnam in AP got close to 800 mm. Even Orissa got very Heavy Rains around 200 mm. The Heavy rains killed  around 50 people in AP.

3rd System - Deep Depression or 2013 Somalia cyclone (Caused the most Deaths)

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The third system of NEM 2013 was Deep Depression (November 8-15). It was a Low Pressure in Comrin Sea near Kanyakumari. It gave good rains to Tirunelveli, Ramanathapuram, Kanyakumari and Tuticorin districts as a Low Pressure. Ramanathapuram and Papanasam got around 400 mm first week of November. The low pressure then intensified into a Deep Depression, nearly became a named cyclone and moved away from Indian coast and made landfall in Somalia in Africa and killed over 140 people. Bandarbeyla and Eyl in Somalia got around 350 mm rainfall while their annual rainfall was just 250 mm. It was one of the worst cyclone to hit Somalia.

4th System - Depression (One day show)

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The 4th one was Depression (Novemeber 13-17). Cuddalore, Nagapattinam and even Chennai got good rains (100-200 mm). But it lasted only one day and as it was a Sheared system rains were not so heavy. It travelled from Philippines to TN only to provide only 1 day of rains.

5th System - Severe Cyclone Helen (Surprise of the NEM)

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The 5th system was Cyclone Helen (November 19-23)  No one including IMD expected it to become cyclone, however it became a cyclone. Then all models predicted it to weaken and take a loop and cross north of Chennai. However it strengthened and crossed Central AP. It was again a complete miss to TN. It caused widespread  destruction in Andhra Pradesh. Vishakapattannam and may other places in AP got over 200 mm rains. Rains were also witnessed in Maharashtra. It has to be the surprise Cyclone of this season.

6th System - Very Severe Cyclone Lehar (No rains/winds - a dud)

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The 6th System was Cyclone Lehar (November 23-28). Hopes in TN soared as all models initially showed TN as landfall. But this cyclone intensified and as usual it moved to AP . It completely gave a miss to TN. It weakened in the sea and crossed Central AP as a very weak system. There were no heavy rains nor any winds. It should be called as the dud of the year.

7th System - Very Severe Cyclone Madi (It made a rare U-turn)

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The 7th System was Cyclone Madi (December 1 to 13). As a low pressure, Ramanathapuram, Tutucorin, Tirunelveli and Kanykumari dts got very good rains with some places getting over 100 mm. However this system also intensified and moved north. All intensified system move north as upper level winds were west to east. But this also weakened and came back to TN in Depression strength. Again it gave rains for only 1 day, Kanyakumari and Villipuram dts got good rains (100 mm). It was also a long lasting cyclone.

8th System - Depression (Spillover of NEM into January 2014)

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A break of one month, the Northeast monsoon spilled over into January. It is a common phenomenon. A Depression (January 3-10) formed near Sri Lanka. It gave around 200-250 mm rainfall in Sri Lanka. Then it entered Gulf of Mannar and gave rains to South TN. Papanasam got around 250 mm rainfall. It was a bonus rains to South TN. Even though the rains were from NEM, it counts as winter rainfall for statistical purpose.

Conclusion

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This sums up the NEM 2013. There was no monsoon rains from regular easterly waves nor did any of the low pressure/depression stay in TN for 2-3 days providing rains like the one Low Pressure which gave bounty to AP.  All the rains were associated with cyclonic systems and as most of then intensified early and thereby moving north and giving a miss to TN. As the cyclones move north the regular NE winds got subdued and thereby resulting in failure of NEM to TN. This is the 1st time in the history we had 4 named cyclones between (October - December).

See you in 2014, NEM Success and failures occur together. From 2005-2011, TN had normal NEM, for past 2 years it was a failure. Lets hope 2014 turns out to be different.

Wettest 24hr rainfall day in Tamil Nadu - Ketti, Nilgris in November 2009

The recent very heavy rainfall over Uttrakhand just reminded me of a severe rainfall event which media ignored completely. Note that the rainfall (3 day accumulated rainfall) was more severe than the one witnessed in Uttrakhand in June 2013-(http://tamilnaduweatherman.blogspot.in/2013/06/dehradun-beats-88-year-old-24hrs.html). It happened in Nilgris district in Tamil Nadu in November, 2009.

Ketti is a small town nestled in Ketti valley. It is located in Coonoor Taluk in the Nilgiris District of the state of Tamil Nadu in India. The valley is the last major valley en route to Ooty along the Ooty-Coonoor highway. Ketti, is located at a height of about 2100 m above mean sea level in Nilgiri (11° 22″ 01′ N & 76° 44″ 32′ E) is a valley surrounded by hills in three directions and opening is only in the ESE direction. It recorded the heaviest rainfall of 820.0 mm in 24 hrs ending 0830 hrs IST on 10 November 2009 which is the all time 24 hrs rainfall record for Tamil Nadu.

Extreme weather events like continuous very heavy rain and floods caused heavy loss of lives and property, damage of roads, banks of rivers in urban and rural areas. Extremely very heavy rainfall over a small areas in the hilly regions make misery in the life of hilly region people due to land slides, soil erosion across roads, rail lines, damage of crops and heavy loss of human lives. In this article the reasons of extreme record rainfall at Ketti in Nilgiri hills and its impacts have been analysed.  

Nilgiris, the hilly region of Tamil Nadu being the part of Western Ghats generally receives more rainfall during SW monsoon than during NE monsoon. On many occasions whenever a system cross Tamil Nadu coast and move inside the land area the interior Tamil Nadu including hilly areas of Nilgiris district receives copious rainfall with isolated extremely very heavy rain in the district. Before 10th November 2009 the heaviest rainfall in 24 hrs recorded in Nilgiri district was 448.3 mm at Kodanad on 15th Nov, 1992. Some of the Storms and Depressions which form in the Bay of Bengal during November and December affect the weather over the Nilgiris district causing heavy rain.

Nilgiris November 2009  - 3 day Rainfall amount in mm

Pre-Cyclone Phyaan

 

A low pressure formed over Comorin area on 07 November 2009 and became a well marked low on 08th. The Comorin area and adjoining Arabian Sea became Depression on 9th, moved towards north and intensified as deep depression on 10th November 2009. Under its influence, heavy to very heavy rainfall occurred in west interior and coastal Tamil Nadu. The Ketti valley which has the average elevation of 2000 m a.s.l. is surrounded by hills except east-southeast side situated in west interior parts of Tamil Nadu. It received extremely heavy rainfall on 10th Nov 2009. The valley faces windward side for NE monsoon and leeward side for SW monsoon. The presence of a depression in Arabian sea (Lat. 11.5° N, Long. 71.5° E at 1200 UTC) on 9th Nov 2009, about 450 km west of Mangalore, influenced the easterlies from Bay of Bengal. The moist air mass entered inland through the land mass of Tamil Nadu. As the depression moved initially in the northerly direction, the strong low level easterly wind mass between Lat. 11 and Lat. 12 deg N rushed towards the centre of the depression/deep depression in Arabian sea through the landmass of Tamil Nadu. The winds from the Bay of Bengal entered into Ketti Valley from south to southeasterly direction and were forced for ascend by the orography. This elevated ascent of moist air triggered the formation of mesoscale vortex over the valley and rained there heavily. Nilgiri Mountains trapped the moisture of easterly wind which condensed into raindrops. Lifting of the unstable moist air by the process of convection lead to cooling and condensation of moisture lead to heavy downpour over the Ketty valley during day and night on 9th as well as early morning hours on 10th. The state revenue officials recorded the rainfall at Ketti, near Ketti railway station, measured good number of rain spells throughout the day and night to avoid overflow of rain water from the rain gauge jar on 9th & 10th of November 2009. Totally 48 people lost their lives in the valley due to this heavy rains. Photos of the impact of heavy rains by Purnan -https://plus.google.com/photos/100054510448395024459/albums/5403518573259751713

Highest 24-hours rainfall in Tamil Nadu (Top 10)

1. 820 mm at Ketti (Nilgirs dt) on November 10, 2009 (Cyclone Phyaan)
2. 709 mm at Vandavasi (Thiruvannamalai dt) on August 5, 1965
3. 656 mm at Orathanadu (Thanjavur dt) on November 27, 2008 (Cyclone Nisha)
4. 528 mm at Thanjavur on November 27, 2008 (Cyclone Nisha)
5. 572 mm at Cuddalore on May 18, 1943
6. 562 mm at Avalanchi (Nilgiris dt) on June 23, 2007
7. 540 mm at Mahabalipuram (Kanchipuram dt) on November 20, 1970 
8. 516 mm at Aanamalai (Coimbatore dt) on November 20,1959
9. 510 mm at Mandapam (Ramanathapuram dt) on April 4, 2005
10. 503 mm at Upper Bhavani (Nilgiris dt) on June 17, 2007

Source: Mausam Docs 
Rainfall Data : Own Compilation

Northeast Monsoon in Tamilnadu

Tamil Nadu, located in southeast Peninsular India receives the major part of its annual rainfall during the northeast monsoon(NEM) season (the three-month period from October to December). While coastal Tamil Nadu receives about 60% of its annual rainfall, interior Tamil Nadu receives about 40–50% of annual rainfall during NEM season (IMD 1973). In comparison with Indian Summer Monsoon (ISM), the NEM is characterized by limited aerial extent and average lesser rainfall amount. During NEM season, Tamil Nadu generally receives rainfall due to the formation of trough of low, cyclonic circulation, easterly waves, low pressure area, depression and cyclonic storm over Bay of Bengal. Because the NE monsoon season is the major rainy season, the vicissitudes of the rainfall of Tamil Nadu state has led to considerable and widespread interest among the public/farmers and in government circles in recent years, in view of the frequent failure of northeast monsoon rainfall (NEMR) over Tamil Nadu and the consequent water scarcity condition.

The NEMR series of Tamil Nadu during 1901–2004 was prepared as follows: The daily rainfall data of 173 stations in Tamil Nadu for the period 1901–1996 was obtained from National Data Center, Pune. Using this daily data, the seasonal rainfall series of Tamil Nadu subdivision for the period 1901–1996 was constructed. The data for the remaining part of the series was collected from the weekly weather report of Area Cyclone Warning Centre, Chennai (Tamil Nadu). As per IMD criteria, excess (deficient) monsoon years for subdivision is defined as whenever the percentage departure of seasonal rainfall from normal of subdivision is more (less) than +19% (−19%). Using this criteria, the excess and deficient NE monsoon years during the period 1901–2004 were identified. During this period there are 22 excess NE monsoon years and 25 deficient NE monsoon years and these are listed below.


Tamil Nadu receives mean rainfall of about 450mm with coefficient of variation 28% during NEMR season. Figure shows the mean rainfall distribution over Tamil Nadu during NEMR season. During the entire NEM season, northeast coastal Tamil Nadu receives rainfall exceeding 600mm. Generally rainfall decreases westwards from coastal area to inland and from north to south. Figure shows the NEMR of Tamil Nadu during the period 1901–2004 expressed as percentage departure from long term normal. Out of 104 years of present study, NEMR over Tamil Nadu was below normal for 54 years (i.e., about 53%). The NEMR over Tamil Nadu was continuously below(above)long term average for a maximum of 9(4) years. Ropelewski and Halpert (1987) found that NEMR over south Tamil Nadu is enhanced (diminished) during the well-known El-Ni˜no episodes that refer to the events of warming (cooling) over central and equatorial Pacific Ocean. Out of 24 years of El-Ni˜no during the period of study, NEMR was normal or excess during 23 years (except during the year 1951).

Source:S Balachandran, R Asokan and S Sridharan, Regional Meteorological Centre, Chennai.
Photo:-My Collections