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Meteorological features associated with flood over eastern India during southwest monsoon 2019 S Bandyopadhyay, H R Biswas, Anand Shankar, Umasankar Das, S D Kotal, Debapriya Roy, Sourish Bondyopadhyay and G K Das IMD, Regional Meteorological Center, Kolkata

This chapter focuses on the meteorological analysis of two instances of flood –one urban flooding over Odisha during 12-14 August 2019 and another in Bihar during 27-30 September 2019.

6.1. Introduction Floods are very common in eastern India during southwest monsoon season. It brings a lot of misery to the people of this region. Monson season 2019 witness massive flood during August and September in eastern India. First instances of urban flood observed over Bolangir district of Western Odisha during 12-14August and second spells of massive flood in Bihar during 26-30September 2019.Patna, the capital city of Bihar has been inundated for several days for this severe flood. A lot of damage to property and few loss of life have been reported.

6.1.1 Physiography of Eastern India Eastern India consists of the six meteorological subdivisions, comprising of five states of eastern India namely West Bengal, Sikkim, Bihar, Jharkhand and Odisha. Sub Himalayan West Bengal (SHWB) and Sikkim form a single subdivision. West Bengal state consists of SHWB and the meteorological subdivision, Gangetic West Bengal (GWB).SHWB & Sikkim is dominated by orography mainly associated with Eastern Himalayas. GWB and Odisha is mainly coastal subdivision near Bay of Bengal whereas Bihar and Jharkhand is landlocked state/subdivision (Fig-6.1(a)).Major river basins in eastern India are Ganga river basin in Bihar and West Bengal area, Odisha has three river basins namely Mahanadi,

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Subarnarekha, Brahmani and Baitarani (Fig-6.1(b)).Majority of tributary rivers of Ganga passing through Bihar and West Bengal.

Fig-6.1(a): Physiogarphy of Eastern India

Fig-6.1(b): Major River Basin of Eastern India Most of the portion of coastal State Odisha is falls very close to southern location of normal position to the monsoon trough during southwest monsoon season. Also many districts and important city of the state lies on the south west sector of monsoon lows/depression moving northwestwards to main land area from Bay of Bengal. Thus Odisha experiences maximum rainfall during south west monsoon season and in addition copious rainfall due to synoptic scale monsoon disturbances, sometimes causes flood in different parts of the state Odisha. Large spatial and temporal variability are exhibited in Indian summer monsoon rainfall in sub-regional scale over Odisha and is very large due to its varied physiographic features. Bolangir city is an important city of Western Odisha and head quarter of Bolangir District. Bolangir district can be characterized as two broad

76 physiographic areas viz., (i) undulating plains with residual hills and (ii) scattered hills and areas with high relief. The undulating plains covers the central and eastern parts of the district the average elevation being 200m to 300m above mean sea level with a general slope towards east.

Fig-6.1(c): Physiogarphy of Odisha

Fig-6.1(d): River basin of Bihar The areas with high relief and high hills are situated in the north western, western and south eastern parts of the district. Bolangir city is located in the northeast parts of the district. A physiographic map of Odisha along with location of Bolangir District/city is depicted in Fig.6.1(c). Orography plays vital role in spatial and temporal rainfall variability within a season. Weatherwise, two important cities of Bolangir district namely Bolangir and Titlagarh are well-known for very high temperature zone of Odisha during summer season. Ever recorded rainfall data(upto 2018) about 70 years reveals that Bolangir was received highest rainfall in 24 hours period, 401.6mm on 30th August, 1982 and this record breaks in

77 monsoon 2019 season. Bolangir has recorded 555.0mm at 0830 hours IST of 14th August, 2019 in past 24 hours. Also, extremely heavy rainfall 263.0 mm was recorded at Bolangir at 0830 hours IST of 13th August, 2019 in past 24 hours. So, within 48 hour period (0830 hours IST of 12th August to 0830 hours IST of 14th August,2019) total 818 mm rainfall which causes floods in different parts of the city and neighbourhood area. Characteristic features of this event have been described in this chapter. There are eight important river basins in Bihar (Figure-6.1(d). These are 1. Gandak, 2. Burhigandak, 3. Bagmati, 4. Adhwara group,5. Kamla Balan, 6. Kosi, 7. Mahananda 8. Ganga Stem in Bihar. The important rivers of North Bihar are Ghaghra, Gandak, BurhiGandak, Kosi and Mahananda etc. which directly flow into river Ganga, whereas Bagmati Adhwara, Kamla- Balan etc. drain into the Ganga through the Kosi. And in South Bihar the important rivers are Punpun, Kiul, Badua, Chandan etc. which also fall ultimately into river Ganga.

6.2. Analysis of exceptionally very heavy rainfall in Bolangir city of western Odisha causing urban floods during 12-14 August 2019

6.2.1 Rainfall Analysis Odisha state is a meteorological subdivision of India has received 7% above normal rainfall 1233mm against normal value of 1155 mm during southwest monsoon season 2019, though in first two months, June and July the rainfall was deficient by 21%. Similarly, Bolangir district has received 16% above normal rainfall 1372mm against normal value of 1180 mm during southwest monsoon season 2019 and upto 31st July 2019(in first two months of the season) rainfall was deficient by 33%( 406 mm rainfall occurred against normal value 602 mm) . Climatologically, annual normal rainfall of Bolangir city is 1418.2 mm and southwest monsoon season (June to September) normal rainfall value is 1215.1mm which is 86% of annual normal value. It is great concern that within 48 hour period (0830 hours IST of 12th August to 0830 hours IST of 14th August,2019) Bolangir city has received total 818 mm rainfall which is 58% and 67% of its annual and monsoon season normal rainfall value respectively. Further out of the 818 mm rainfall, 718 mm rainfall occurred in 24hours period from 12th August Evening (1200 UTC) to 13th August Evening (1200 UTC) which might have cause more vulnerable situation in Bolangir city. The highest rainfall in a day recorded during last 10 years over Bolangir city is shown in Table 6.1. It is observed that during last 10years there is no extreme rainfall (≥20cm) event over Bolangir city. The overall distribution of rainfall including state raingauge station occurred in past 24 hours recorded at 0830 hours IST of 14th August,2019 is also depicted in Fig. 6.2. It shows that heavy rainfall zone mostly confined in central parts of western Odisha with maximum core in Bolangir.

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Fig. 6.2 : Blockwise rainfall distribution in past 24 hours recorded at 0830 hrs IST of 14th August,2019 (The rainfall map obtained from Odisha State Disaster Management Authority (OSDMA), Govt. of Odisha).

Table 6.1 Highest rainfall recorded in 24 hours period in different year over Bolangir city during last 10 years. Year Highest Rainfall in Date 24 hours (in mm) 2010 70.0 25-07-2010

2011 128.3 26-08-2011 2012 111.0 21-06-2012 2013 197.8 23-07-2013 2014 148.0 29-07-2014 2015 86.0 09-01-2015 2016 170.4 07-02-2016 2017 107.0 17-07-2017 2018 92.8 27-08-2018 2019 555.0 14/08/2019

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6.2.2 Synoptic Features Under Influence of a cyclonic circulation over northeast Bay of Bengal and neighbourhood, a low pressure area has formed over northwest Bay of Bengal adjoining West Bengal and Bangladesh coasts with the associated cyclonic circulation extending upto 7.6 km above mean sea level tilting southwest wards with height on 12th (0300 UTC) August,2019. It lay over southern parts of Gangetic West Bengal adjoining north Odisha with the associated cyclonic circulation extending upto 7.6 km above mean sea level tilting southwest wards with height at 0300 UTC of 13th August,2019. It moved west northwestwards and lay over northwest parts of Chhattisgarh with the associated cyclonic circulation extending upto 7.6 km above mean sea level tilting southwest wards with height at 0830 hours IST of 14th August,2019. Mean sea level chart of13th August,2019 evening have been depicted in Fig.6.3 as representative and ECMWF model reanalysis wind charts of 850hPa level overlaid on toposheet for 12th ,13th and 14th August (00UTC) have been depicted in Fig.6.4.

Fig. 6.3 : Mean sea level pressure chart of 1200 UTC of 13th August,2019

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Fig. 6.4 : ECMWF model reanalysis wind charts of 850hPa level overlaid on toposheet for 12th ,13th and 14th (00UTC) August 2019

It is observed that central parts of western Odisha falls on south west and left forward sector of the low pressure system. Moreover, moist air striking towards hill slope located to the southeast side of Bolangir district. Thus Bolangir city and its neighbourhood area fall in the strong moisture convergence zone and southwest sector of a low pressure system tilting south-westwards with height. It may cause exceptionally very heavy rainfall over this area. ECMWF model 850 hPa vorticity analysis reflected highest rainfall area (Bolangir and its neighbourhood) was in the edge points of higher values of low level vorticity which may be due to tiling of cyclonic circulation associated with the low pressure system. Insat 3D Satellite images of different times (12th August 1200 UTC to 13th August 0900 UTC) are depicted in Fig. 6.5.

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(a) 12.08.2019(12UTC) TIR - 1 (b) 12.08.2019(22UTC) TIR- 1

(c )13.08.2019(02UTC) TIR -1 (d) 13.08.2019(09UTC) TIR -1

Fig. 6.5 : INSAT 3D satellite Thermal Infrared -1(TIR-1) (10.8µm) images for different time during 12-13 August,2019

The cloud pattern indicates that convective clouds were spread over Western Odisha and adjoining area in association with the low pressure system, but convective clouds persisted for longer period over Bolangir district and neighbourhood area and convective clouds clusters’ centre was located on the northeastern side of the District (Bolangir city area). Also average value of daily OLR (12th& 13th) was less than 100 WM-2 (Fig.6.6), indicated persistence of convective clouds for longer period over central parts of western Odisha.

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Fig. 6.6 : INSAT 3D satellite data derived daily average OLR (WM-2 ) value for (a)12th - 13th August,2019 and (b)13th – 14th August 2019.

6.2.3 Damages due to exceptionally very heavy rainfall and floods

As per different media report, due to exceptionally very heavy rainfall in the Bolangir city and neighbourhood area most of the municipal area of Bolangir city were under water, rainwater flowing the road and entered in houses. In the Bolangir city and neighbourhood low lying area worst affected by local flood and many houses washed away. Local administration evacuated about 15000 people from Bolangir municipal area and gave safe shelter. Photographs of media clip are depicted in Fig. 6.7.

Fig. 6.7 : Photographs of media clip of flood and damage in Bolangir city

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6.2.4 Monitoring of the system and weather Warnings The low pressure system was closely monitored by Meteorological Centre, Bhubaneswar under guidance of RMC Kolkata and NWFC, New Delhi. Information on Synoptic Situation and heavy rainfall warning and advisories, nowcast issued to various authorities of Govt. of Odisha, Principal Secretary, Revenue & Disaster Management, Principal Secretary, Dept. of Agriculture, Principal Secretary, Department of Water Resources, Special Relief Commissioner (SRC), M.D., OSDMA, Govt. of Odisha, RDC, Central Division/ Southern Division/ Northern Division, AIR Cuttack / Doordarshan , print and electronic media etc. QPF and daily rainfall status was provided to Central Water Commission. All the mode of communication like telephone, E-mail, Websites, Whatsapp / SMS, regional and national electronic and print media has been used for dissemination of advisory and warning. The extent of damages due to such natural disaster event was mitigated with the advent of early warnings and active disaster response system of state disaster authority.

6.3 Analysis of exceptionally very heavy rainfall in Bihar causing urban floods in Patna and adjoining area during 26-30 September 2019 6.3.1 Synoptic Situation associated with massive flood in Bihar during 27-30 September 2019 Major synoptic situation associated with massive flood in Bihar during 27-30 September 2019 is depicted in Fig.6.8 and 6.9.The mean sea level pressure (MSLP) pattern (Fig. 6.8) during 26-30 Sept 2019 whereas Fig. 6.8 and 6.9 shows the lower level wind pattern and absolute humidity respectively. During 26-30 September 2019 a break monsoon like situation observed with strong pressure gradient along with east west trough from UP to NMMT with cyclonic circulation over Bihar and adjoining E UP (Fig. 6.9) with a very strong vorticity (Fig. 6.10) over the region.

Fig. 6.8(a): MSLP on 26.09.2019 Fig. 6.8(b): MSLP on 27.09.2019

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Fig. 6.8(c): MSLP on 29.09.2019 Fig 6.8(d): MSLP on 30.09.2019 Fig. 6.8 : MSLP analysis during 26-30September 2019

Fig. 6.9(a): Wind on 26.09.2019 Fig. 6.9(b): Wind on 27.09.2019

Fig. 6.9(c): wind on 29.09.2019 Fig. 6.9(d): wind on 30.09.2019 Fig. 6.9 : Wind during 26-30 September 2019

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Fig. 6.10(a): Absolute Vorticity on 26.09.2019 Fig 6.10(b): Absolute Vorticity on 27.09.2019

Fig. 6.10(c): Absolute Vorticity on 29.09.2019 Fig 6.10(d): Absolute Vorticity on 30.09.2019 Fig. 6.10 : Absolute Vorticity during 26-30 September 2019

The whole system was almost stagnant over the region with some intensification. Along with above synoptic system there was a strong moisture incursion from Bay of Bengal during this period leading to massive flood over Bihar during 27-30 September 2019 (Fig. 6.11).

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Fig. 6.11(a) : Satellite Picture of 28.09.2019

Fig. 6.11(b) : Satellite Picture of 29.09.2019 Fig. 6.11 : Satellite picture of Bihar Flood during 26-30 September 2019

6.3.2 Rainfall associated with Bihar flood Rainfall associated with flood in Bihar during 26-30 September 2019 are shown in Fig.12 and 13.Heavy to very heavy rainfall at many places with extremely heavy rainfall at few places lead to vigorous monsoon activity during 27-30 September 2019 with excess rainfall in the month of September (+82%) over Bihar leading to massive flood mainly urban area of Patna and its suburban area of Danapur. The rainfall during 27-30 September 2019 is given below (7 cm and above).

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27.09.2019 Bhore (Gopalganj) 13, Rosera (Samastipur) 7, Pusa (Samastipur) 7, Rafiganj (Aurangabad) 7 28.09.2019 Jandhaha (Vaishali) 23, Rajauli (Nawada) 22, Rosera (Samastipur) 17, Tekari (Gaya) 17, Goraul/Doli (Vaishali) 16, Bhagalpur (Bhagalpur) 13, Basua (Supaul) 13, Sripalpur (Patna) 12, Bihpur (Bhagalpur) 11, Hisua (Nawada) 11, Kodawanpur/C.B Ii (Begusarai) 11, Sabour (Bhagalpur) 10, Patna Aerodrome (Patna) 10, Buxar (Buxar) 9, Makhdumpur (Jahanabad) 9, Saraiya (Muzaffarpur) 9, Samastipur (Samastipur) 9, Rewaghat (Muzaffarpur) 9, Deo (Aurangabad) 9, Mahua (Vaishali) 9, Jamui (Jamui) 9, Nawada (Nawada) 8, Supaul (Supaul) 8, Mushari (Muzaffarpur) 8, Madhipura (Madhepura) 8, Murliganj (Madhepura) 7, Sono (Jamui) 7, Morwa/Tajpur (Samastipur) 7, Barh (Patna) 7, Jhajha (Jamui) 7, Gaya Aero (Gaya) 7, Bodh Gaya (Gaya) 7, Cheria B.Pur 1 (Begusarai) 7, Daudnagar (Aurangabad) 7, Kessariah (East Champaran) 7, Mohania (Bhabua) 7, Rafiganj (Aurangabad) 7, Hasanpur (Samastipur) 7, Islampur (Nalanda) 7, Aurangabad (Aurangabad) 7, Benibad (Darbhanga) 7, Bhore (Gopalganj) 7, Pusa (Samastipur) 7 29.09.2019 Rosera (Samastipur) 29, Bihpur (Bhagalpur) 21, Koilwar (Bhojpur) 21, Basua (Supaul) 20, Hasanpur (Samastipur) 17, Sahebpur Kanal (Begusarai) 16, Patna Aerodrome (Patna) 15, Cheria B.pur 1 (Begusarai) 15, Jhanjharpur (Madhubani) 14, Khagadia (Khagaria) 14, Katoria (Banka) 13, Monghyr (Monghyr) 13, Marhaura/amnaur (Saran) 13, Bhabhua (Bhabua ) 13, Ekangersarai (Nalanda) 13, Sono (Jamui) 13, Bahadurganj (Kishanganj) 13, Madhipura (Madhepura) 13, Bhagalpur (Bhagalpur) 12, Barhiya (Lakhisarai) 12, Chenari (Rohtas) 12, Kodawanpur/c.b Ii (Begusarai) 12, Sripalpur (Patna) 12, Mohania (Bhabua ) 12, Parbatta (Khagaria) 12, Hisua (Nawada) 12, Gogri (Khagaria) 12, Bodh Gaya (Gaya) 12, Garhi (Jamui) 12, Supaul (Supaul) 11, Vaishali (Vaishali) 11, Barh (Patna) 11, Parsa (Saran) 11, Kudra (Bhabua ) 11, Sherghati (Gaya) 11, Udai Kishanganj (Madhepura) 11, Sirmari B.pur (Saharsa) 10, Tribeniganj (Supaul) 10, Bihta (Patna) 10, Sabour (Bhagalpur) 10, Purnea (Purnea) 10, Katihar North (Katihar) 10, Banka (Banka) 10, Mahua (Vaishali) 10, Manihari (Katihar) 10, Daudnagar (Aurangabad) 10, Bikram (Patna) 9, Murliganj (Madhepura) 9, Suryagadha (Lakhisarai) 9, Nawada (Nawada) 9, Galgalia (Kishanganj) 9, Morwa/tajpur (Samastipur) 9, Gaya Aero (Gaya) 9, Islampur (Nalanda) 9, Chapra (Saran) 9, Maheshi (Saharsa) 9, Nirmali (Supaul) 9, Goraul/doli (Vaishali) 9, Rajauli (Nawada) 9, Jhajha (Jamui) 9, Dhengraghat (Purnea) 9, Darbhanga (Darbhanga) 9, Buxar (Buxar) 9, Indrapuri (Rohtas) 8, Barahara (Bhojpur) 8, Kessariah (East Champaran) 8, Rewaghat (Muzaffarpur) 8, Kursela (Katihar) 8, Rafiganj (Aurangabad) 8, Phulparas (Madhubani) 8, Saraiya (Muzaffarpur) 8, Jalalpur (Saran) 7, Deo (Aurangabad) 7, Baltara (Khagaria) 7, Makhdumpur (Jahanabad) 7, Sheikhpura (Sheikhpura) 7, Kamtaul (Darbhanga) 7, Gopalganj (Gopalganj) 7, Saulighat (Madhubani) 7, Taibpur (Kishanganj) 7, Forbesganj (Araria) 7, Thakurganj (Kishanganj) 7, Sursand (Sitamarhi) 7 30.09.2019 Rosera (Samastipur) 25, Udai Kishanganj (Madhepura) 24, Baltara (Khagaria) 22, Chargharia (Kishanganj) 20, Purnea (Purnea) 17, Bihpur (Bhagalpur) 17, Kursela (Katihar) 16, Parbatta (Khagaria) 15, Murliganj (Madhepura) 15, Manihari (Katihar) 15, Hasanpur (Samastipur) 14, Tribeniganj (Supaul) 14, Katihar North (Katihar) 14, Sirmari B.Pur (Saharsa) 13, Gogri (Khagaria) 13, Khagadia (Khagaria) 13, Dhengraghat (Purnea) 13, Madhipura (Madhepura) 12, Forbesganj (Araria) 12, Maheshi (Saharsa) 12, Kodawanpur/C.B Ii (Begusarai) 12, Basua (Supaul) 11, Nirmali (Supaul) 11, Cheria B.Pur 1 (Begusarai) 11, Jhanjharpur (Madhubani) 11, Ekangersarai (Nalanda) 11, Araria (Araria) 10, Birpur (Supaul) 10, Bhimnagar (Supaul) 9, Bhagalpur (Bhagalpur) 9, Bikram (Patna) 9, Monghyr (Monghyr) 9, Patna Aerodrome (Patna) 9, Barahara (Bhojpur) 9, Morwa/Tajpur (Samastipur) 9, Jahanabad (Jahanabad) 9, Sahebpur Kanal (Begusarai) 9, Buxar (Buxar) 8, Mahua (Vaishali) 8, Jandhaha (Vaishali) 8, Sripalpur (Patna) 8, Islampur (Nalanda) 7, Koilwar (Bhojpur) 7, Sabour (Bhagalpur) 7, Siswan (Siwan) 7, Colgaon (Bhagalpur) 7

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Fig. 6.12(a) : Realized rainfall on 26.09.2019 Fig. 6.12(b) : Realized rainfall on 27.09.2019

Fig. 6.12(c) : Realized rainfall on 29.09.2019 Fig. 6.12(d) : Realized rainfall on 30.09.2019 Fig 6.12 : Rainfall distribution during 26-30 September 2019

6.3.3 Damage due to the Flood during 26-30 September 2019 As per Bihar Disaster Management Department report, Damage to property and causalities caused by flood are as follows: (A) Affected areas due to flood: Districts- 26Nos (Araria,Kishanganj,Madhubani,East Champaran,Sitamari,Sheohar,Supaul,Darbhanga,Muzaffarpur,Saharsa,Katihar,Purnia,West- Champaran,Buxar,Bhojpur,Samastipur,Lakhisarai,Begusarai,Khagaria,Bhagalpur,Munger,P atna,Saran,Vaisali,Nawada and Jehanabad) (B) Number of village/panchayat affected: 1724 (panchayats) (C) Population affected: 104 lakhs (D). Human death toll : 130 Nos

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Fig. 6.13(a) : rainfall departure 27.09.2019 fig. 6.13(b) : rainfall departure 28.09.2019

Fig. 6.13(c) : rainfall departure 29.09.2019 fig. 6.13(d) : rainfall departure 30.09.2019 Fig. 6.13 : Rainfall departure during 26-30 September 2019

6.3.4. Monitoring of Meteorological condition by MC Patna The weather system associated with above flood was closely monitored by Meteorological Centre, Patna under guidance of RMC Kolkata and NWFC, New Delhi. Information on Synoptic Situation and heavy rainfall warning and advisories, nowcast issued to various authorities of Govt. of Bihar, Principal Secretary, Revenue & Disaster Management, Principal Secretary, Dept. of Agriculture, Principal Secretary, Department of Water Resources, Doordarshan, print and electronic media etc. QPF and daily rainfall status was provided to Central Water Commission. All the Senior Officer of Govt of Bihar along with media has been brief regularily. Several press release has been issued regarding this

90 severe weather. All the mode of communication like telephone, E-mail, Websites, Whatsapp /SMS, regional and national electronic and print media has been used for dissemination of advisory and warning. The extent of damages due to such natural disaster event was mitigated with the advent of early warnings and active disaster response system of state disaster authority.

6.4. Conclusions

1. During Southwest Monsoon season 2019 eastern India witness massive flood over Odisha and Bihar. 2.Flood over Bolangir area of Odisha during 12-14 August 2019 was due to to synoptic scale system-monsoon low over Northwest Bay of Bengal and associated cyclonic circulation tilted southwestwards with height over the area along with strong moisture convergence and local Physiographic features. 3. Whereas Bihar flood was associated with East-west trough at mslp from UP to NMMT region with cyclonic circulation at lower level over Bihar with strong moisture incursion from Bay of Bengal. Whole system was persisted over the region for four days during 26-30 September 2019. 4. Widespread damage to the agricultural crops and loss of life has been reported in Bihar due to the flood. 5. Issue of weather forecast/warnings/QPF over river basins well in advance and its transmission by all means of communications like telephone/fax, internet, website, e-mail, whatsapp to the concerns State Government disaster Manager, CWC along with personal briefing to Senior Officer of Government and media by MC Bhubaneswar and MC Patna were very much effective for management of adverse disaster situation.

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