MetraWeather forecasters predicted the development and track of Tropical Cyclone Roanu

Tropical Cyclone 'Roanu' NOOA Himawari 8

One key region for MetraWeather’s marine forecasting bench is the Bay of Bengal. The largest bay in the world, it forms the north-eastern part of the Indian Ocean. Roughly triangular, it is bordered mostly by India and Sri Lanka to the west, Bangladesh to the north, and Myanmar and the Andaman and Nicobar Islands to the east.

On Monday 16 May 2016, MetraWeather Lead Meteorologist Raveen Das analysed a tropical depression about 195 km to the northeast of Colombo, Sri Lanka. The analysis was based on a persistent convective cloud signature, satellite-based wind observations and modelling information.

The overall environment was assessed to be favourable for the depression to develop in to a tropical cyclone but land interaction was expected to delay the intensification process. The depression was forecast by MetraWeather to track northwards over land during the following 24 to 42 hours, move offshore over very warm waters east of Tamil Nadu, and then evolve into a tropical cyclone on the 18th of May.

The MetraWeather cyclone track forecast had ‘Roanu’ moving northeast and making landfall in Bangladesh over the coming weekend.

By Friday 21 May, a Bangladesh disaster management ministry spokesman said some 500,000 people had been evacuated into 3500 shelters, and aviation authorities suspended flight operations at Chittagong’s Shah Amanat International Airport.

The Bangladesh Meteorological Department issued a danger signal for four sea ports, as well as Bangladesh's main port of Chittagong ordering 19 ships to leave the port and anchor in the outer anchorage. The Bangladesh Inland Water Authority ordered suspension of water-based transport and ferry services in the internal riverine networks.

Bangladesh is vulnerable to cyclones because of its location at the triangular-shaped head of the Bay of Bengal, the sea-level geography of the coastal area and high-population density. The shape of the Bay of Bengal funnels water leading to storm surges. About 40 percent of the world's storm surges occur in the bay.

Two of the world’s deadliest cyclones struck coastal regions in 1970 and 1991 claiming some 500,000 and almost 140,000 lives respectively. Tropical Cyclone ‘Maria’ in 1991 slammed into South East Bangladesh with winds reaching 250 km/h (155 mph) and a 6 metre (20 feet) storm surge that left 10 million homeless.

Tropical Cyclone ‘Roanu’ sadly did result in a loss of lives in Sri Lanka, India and Bangladesh, but disaster risk reduction measures reportedly did mitigate many of the risks and help reduce the cyclone’s impact on vulnerable communities.

Neighbouring Myanmar (which is also susceptible to cyclonic weather events) and Bangladesh are thought to have significant, undeveloped offshore oil and gas reserves.

As the severity of tropical cyclones escalates due to climate change, oil and gas companies operating offshore need to be cognisant of the challenges that severe weather can pose to their staff, operations, assets and reputations. It is crucial to receive marine weather guidance from expert forecasters certified to provide tropical cyclone forecasting by the UN World Meteorological Organisation.

Raveen Das is a Lead Meteorologist and Tropical Cyclone Specialist with MetraWeather and MetService. He holds a Bachelor of Science Degree from the University of the South Pacific in Fiji, as well as WMO Class I Meteorologist Certification, and has more than 20 years of regional and tropical forecast experience.

Animation courtesy NOAA and Himawari 8

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