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Cyclone Roanu

North Indian Ocean cyclone in 2016

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Through Sri Lanka, Bangladesh and Andhra Pradesh

The storm was responsible for 105 deaths in Sri Lanka and another 30 deaths in Bangladesh. A further 99 persons in Sri Lanka were reported missing. Damage throughout Sri Lanka reached US$2 billion. Roanu also brought torrential rainfall to the Indian states of Tamil Nadu, Andhra Pradesh, Kerala and Odisha as it drifted in a generally northeastward direction, close to the coast.

Meteorological history

Under the influence of a trough, a low-pressure area formed over the Bay of Bengal on 14 May. It slowly consolidated as it paralleled the east coast of Sri Lanka, prompting the India Meteorological Department (IMD) to classify it as a depression on 17 May. Late the same day, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert (TCFA), soon after which the JTWC upgraded the system to a tropical storm. Simultaneously, the IMD upgraded the storm to a Deep Depression, prompting the issuance of cyclone warnings for the states of Andhra Pradesh and Odisha. On 19 May, the IMD reported that the storm had reached cyclonic storm intensity, and assigned it the name Roanu.

At the time, Roanu was tracking slowly northward along the northern periphery of a subtropical ridge located over the Malay Peninsula. Despite favorable outflow and warm sea surface temperatures (SSTs) reaching 31 °C (88 °F), its proximity to land and moderate vertical wind shear kept the storm from intensifying rapidly. The diurnal temperature variation over land and the persistent wind shear began to affect the deep convection obscuring the low-level circulation center (LLCC). In the late hours of that day, Roanu showed a weakening trend after most of the convection covering the LLCC was sheared off. During that time, Roanu was located approximately 150 kilometres (93 mi) from Visakhapatnam. However, the wind shear soon decreased, and the storm reestablished deep convection over and around the LLCC, forming a central dense overcast in a period of 6 hours. SSMIS imagery revealed tightly curved rainbands wrapped into the LLCC. As a result, Roanu re-intensified as it accelerated east-northeastwards towards the coast of Bangladesh, and reached its peak intensity with winds of 85 km/h (55 mph) and a minimum central pressure of 983 hPa (mbar; 29.03 inHg). On 21 May, Roanu made landfall just northwest of Chittagong, Bangladesh. Continuing to accelerate inland, Roanu steadily weakened and degenerated into a remnant low on the next day.

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