Deep depression over BoB was the first depression over the north Indian Ocean duringthe monsoon season, 2021.

 New Delhi, chhttisgarh.

Asal Baat News.

India Meteorological Department (IMD) maintained round the clock watch over the north Indian Ocean and the system was monitored since 2nd September, about 9 days prior to the formation of LPA over eastcentral & adjoining northeast BoB on 11th and 10 days prior to formation of depression on 12th. The cyclone was monitored with the help of available satellite observations from INSAT 3D and 3DR, polar orbiting satellites and available ships & buoy observations in the region. The system was also monitored by Doppler Weather RADAR (DWR) Paradip (Odisha). Various numerical weather prediction models run by Ministry of Earth Sciences (MoES) institutions, global models and dynamical-statistical models were utilized to predict the genesis, track, landfall and intensity of the system. A digitized forecasting system of IMD was utilized for analysis and comparison of various models’ guidance, decision making process and warning products generation. 

 A low pressure area (LPA) formed over eastcentral and adjoining northeast Bay of Bengal 

(BoB) in the early morning (0530 hrs IST) of 11th September, 2021. It lay as a well marked low pressure area (WML) over northwest and adjoining westcentral BoB in the early morning 0530 hours IST) of 12th

 Under the favourable environmental and oceanic conditions, it concentrated into a 

depression over northwest BoB and adjoining Odisha coast in the evening (1730 hrs IST) of 12th

 Moving west-northwestwards, it intensified into a deep depression over northwest BoB very 

close to Odisha coast in the early morning (0530 hrs IST) of 13th and crossed north Odisha 

coast, close to south of Chandbali between 0530 & 0630 hrs IST as a deep depression with 

maximum sustained wind speed of 30 knots (50-60 kmph).

 Continuing to move further west-northwestwards, it weakened into a depression over north 

Chhattisgarh & adjoining north interior Odisha in the morning (0830 hrs IST) of 14th and into 

a WML over northeast Madhya Pradesh & neighbourhood in the early morning (0530 hrs 

IST) of 15th

 The observed track of the system is presented in Fig. 1. 

2. Salient features: 

i. Deep depression over BoB was the first depression over the north Indian Ocean duringthe monsoon season, 2021.

ii. It caused active to vigorous monsoon conditions leading to extremely heavy rainfall at a few places over Odisha on 12th & 13th, at isolated places over Chhattisgarh on 13th and 

over East Madhya Pradesh on 14th. In conjunction with another low pressure area over 

Gujarat, extremely heavy rainfall at a few places also occurred over Saurashtra and north 

Konkan on 13th September. Low level convergence of wind & enhanced moisture 

incursion from the Bay of Bengal in association with a trough extended eastwards across 

the system also caused extremely heavy rains at isolated places over West Bengal on 

14th September.

iii. A few of the rainfall amounts such as Astaranga & Kakatpur-53 cm-each, Balikuda-44cm, 

Kantapada-38cm, Niali-37cm, Puri-34 cm, Gop & Satyabadi-33cm-each, Ragunathpur-32 

cm were recorded over Odisha on 12th

, Talcher – 39 cm, Birmaharajpur – 37cm, 

Tikarapara – 35cm in Odisha on 13th and Lodhika – 52cm, Visavadar – 47cm, Kalavad –

41cm in Saurashtra had been exceptionally heavy. These extreme rainfall events caused 

Flash floods & Urban flood situation in major Districts including Puri, Khorda, 

Jagatsinghpur, Kendrapara, Subarnapur & Angul in Odisha and Rajkot & Jamnagar in

Saurashtra. As per the report from Central Water Commission Mahanadi river is in spate 

over some parts of Odisha, as on today.

iv. It had a total life period of 60 hours against the average life period (1990-2013) of 75 

hours of deep depression category in monsoon season over the BoB.

v. The system had track length of about 545 km. 

Monitoring: 

India Meteorological Department (IMD) maintained round the clock watch over the north Indian Ocean and the system was monitored since 2nd September, about 9 days prior to the formation of LPA over eastcentral & adjoining northeast BoB on 11th and 10 days prior to formation of depression on 12th. The cyclone was monitored with the help of available satellite observations from INSAT 3D and 3DR, polar orbiting satellites and available ships & buoy observations in the region. The system was also monitored by Doppler Weather RADAR (DWR) Paradip (Odisha). Various numerical weather prediction models run by Ministry of Earth Sciences (MoES) institutions, global models and dynamical-statistical models were utilized to predict the genesis, track, landfall and intensity of the system. A digitized forecasting system of IMD was utilized for analysis and comparison of various models’ guidance, decision making process and warning products generation. Typical satellite and radar imageries at the time of crossing Odisha coast are presented in Fig.2.

Fig.1: Observed track of deep depression over northwest BoB during 12th-15th Sep, 2021

each, Paddhari - 18, Ranavav -16, Talala & Mendarda – 15 each, Porbandar - 14, Malia -

13, Vanthali, Jamnagar, Jamjodhpur & Upleta – 12 each, Dhrol, Manavadar, Vadia & 

Bhesan – 11 each, Lalpur, Kutiana, Bhanvad & Kalyanpur – 10 each, Jetpur, Tankara & 

Jamnagarkvkaws – 9 each, Una, Veraval & Diu (dist Diu) - 8 each and Gir Gadhada & Dwarka 7 each.

Chhattisgarh:

Gariabund-20, Basana-19, Magarlod, Bagbahara & Chhura-14 each, Kurud-13, Rajim, 

Mahasamund & Saraipali-11 each, Raipur & Labhandih-10 each, Patan-9, Arang & 

Mana-raipur, Kartala & Abhanpur 8 each and Sakti, Bilaigarh, Saja & Gandai-7 each

15th September

Gangetic West Bengal:

Kharagpur-28, Midnapore-28, Kalaikunda & Mohanpur-27 each, Midnapore-26, Uluberia 

AWS-20, Contai & Diamond Harbour-18 each, Durgachack-17, Dum Dum-16, MO Salt 

Lake-14, Barrackpur-13, Lalgarh & Burdwan -12 each, Jhargram -11, Alipore & AMFU 

Kakdwip-10 each, Harinkhola, Canning & Digha-9 each, Bagati-8 and Kalyani -7 

Chhattisgarh:-Pendra Road-18, Dhamtari-15, Marwahi-13, Gurur-12, Dondilohara &

Mainpat-11each, Pendra, Jashpurnagar & Mungeli-10, Balod, Dongargaon, Lakhanpur & 

Kota-9, Gariabund, Gundardehi, Mohla, Chhuikhadan, Surajpur, Katghora & Bemetara-8

each and Duldula, Batoli, Khairagarh, Ambagarh Chowki, Rajpur, Pusaur, Gandai, 

Baloda Bazar, Sarangarh & Manora-7each.

West Madhya Pradesh:-Khirkiya—11 and Budhni & Bhimpur-7 each, 

East Madhya Pradesh:

Amarkantak-24, Lanji-13, Balaghat--10, Karanjia-9, Kotma-8 and Channodi & Lalburra-7

each.

Odisha: Chandanpur-15, Ghatagaon-13, Bhograi & Sundargarh-12, Kakatpur-11, 

Deogaon & Banaigarh-10, Lathikata & Bangiriposi-9, Jamsolaghat, Gurundia, Lahunipara 

& Jharsuguda-8, Gunupur & Jaleswar-7

Gujarat Region:-Mangrol-16 and Mahuva, Chhota Udepur-7 each.