A coupled hydrodynamic modeling system for PHAILIN cyclone in the Bay of Bengal P.L.N. Murty a , K.G. Sandhya a , Prasad K. Bhaskaran b, ⁎, Felix Jose c , R. Gayathri b , T.M. Balakrishnan Nair a , T. Srinivasa Kumar a , S.S.C. Shenoi a a Earth System Science Organisation (ESSO)-Indian National Centre for Ocean Information Services (INCOIS), Hyderabad 500 090, India b Department of Ocean Engineering and Naval Architecture, Indian Institute of Technology Kharagpur, Kharagpur 721 302, India c Department of Marine & Ecological Sciences, Florida Gulf Coast University, Fort Myers, FL 33965, USA abstract article info Article history: Received 30 May 2014 Received in revised form 8 August 2014 Accepted 11 August 2014 Available online xxxx Keywords: Coupled model Storm surge Wave setup Cyclone Phailin East coast of India is characterized by low to medium topography and an extensive network of major estuaries, bays, mangrove creeks, rivers and tidal inlets that permit inland flooding during tropical cyclones. A coupled wave + surge hydrodynamic modeling system (ADCIRC + SWAN) is implemented to simulate storm surge, still water level elevation and wave induced setup associated with ‘Phailin’, a very severe cyclonic storm that made landfall in the Odisha State, east coast of India, during October, 2013. The coupled model provides a realistic description on the dynamic interaction of tides, wind, waves and currents, which is critical for operational needs. The study assesses the role of wave-induced setup on the net water level elevation using time varying wave ra- diation stress that is dynamically updated in the coupled model run. Numerical experiments are carried out for both storm surge alone and coupled mode versions. Dependent upon complex bathymetry and coastal geometry, inclusion of wave-induced setup in coupled runs results in an additional 23–36% increase of peak surge relative to an uncoupled, surge-tide simulation. The significant wave height from coupled model also shows an excellent match with observed wave heights from a wave-rider buoy located off the Odisha coast. The comparison of surge residuals between model and observation also exhibits a good match. The study highlights the importance of having a coupled wave-hydrodynamic model for operational needs in the north Indian Ocean. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Cyclone ‘Phailin’ in Thai language meaning “sapphire” was one of the strongest tropical cyclones ever recorded over the northern Indian Ocean basin (Bernhard et al., 2013). Next only to the 1999 Odisha super cyclone, in terms of maximum wind speed and central pressure, Phailin made landfall at Odisha coast, along the east coast of India on October 2013. This cyclone originated as a tropical depression in the Gulf of Thailand on October 4. Later it crossed over Malay Peninsula and entered into Andaman Sea (eastern Indian Ocean) on the 6th of October, 2013. It continued its journey through Indian Ocean in a west–northwest direction. On October 10, ‘Phailin’ intensified rapidly and became a cyclone equivalent to a category 1 hurricane. On the next day, still moving over warm tropical Indian Ocean, it exploded into a super cyclone, equivalent to a category 5 hurricane. During a period of 24 h, wind speed increased from 83 km h -1 to 213 km h -1 . The system started to weaken as it approached Odisha coast of India and made landfall at Gopalpur (see cyclone track details in Fig. 1) around 17 UTC on October 12, 2013. The maximum sustained wind speed during land- fall was about 215 km h -1 with central pressure of 940 mb. Further details on the intensification and movement of ‘Phailin’ are available in the IMD (2013). The severe cyclonic storm left behind a wide swath of damaged infrastructure, flooding of agricultural farmlands, wide- spread death of livestock and a few instances of human loss along coast- al Odisha and parts of northeastern Andhra Pradesh. Timely warnings and alertness by the national disaster management authorities and massive evacuation efforts were very effective in minimizing human loss, as compared to the death toll during 1999 Odisha Super Cyclone. East coast of India encompasses a network of highly productive estu- aries and mangrove creeks. Many larger cities are located along this coast, viz; Chennai, Vijayawada, Visakhapatnam, Gopalpur, Paradeep, Puri, and Kolkata. The low to medium elevation open coast is highly vul- nerable to storm surges resulting from the landfall of tropical cyclones that are originating in the Bay of Bengal. Along the east coast of India, between Paradeep and Balasore in Odisha state, and between Bapatla and Kakinada in the Andhra Pradesh, coastal zone adjoining the Bay of Bengal is classified as a very high-risk zone, in terms of coastal vulnerability from natural calamities. Several case studies were reported Coastal Engineering 93 (2014) 71–81 ⁎ Corresponding author at: Department of Ocean Engineering & Naval Architecture, Indian Institute of Technology Kharagpur, Kharagpur -721 302, West Bengal, India. Tel.: +91 3222 283772; fax: +91 3222 255303. E-mail addresses: pkbhaskaran@naval.iitkgp.ernet.in, prasad.bhaskaran@gmail.com (P.K. Bhaskaran). http://dx.doi.org/10.1016/j.coastaleng.2014.08.006 0378-3839/© 2014 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Coastal Engineering journal homepage: www.elsevier.com/locate/coastaleng