Monday 14 October 2013

Cyclone Phailin kills 23 people in Orissa and Andhra Pradesh.

Twenty three people are now known to have died after Cyclone Phailin made landfall in Orissa State, India, slightly after 9.00 pm local time on Saturday 12 October 2013, brining with it winds of up to 220 km per hour and widespread flooding. This is the most severe tropical storm to hit India since 1999, when a cyclone killed around 10 000 people in Orissa alone. Officials in India are attributing the lower death toll from this week's storm to better prediction systems, which allowed for the evacuation of around 873 000 people from the worst affected areas, the largest such evacuation India has ever attempted.

A fishing village on the Indian coast affected by Cyclone Phailin. Getty Images.

Of the known fatalities 21 died in Orissa State and the remaining two in Andhra Pradesh. The storm is also believed to have destroyed unharvested rice worth around ₨240 billion (slightly under US$ 4 billion), and damaged or destroyed around 234 000 homes. A cargo ship, the Panama registered MV Bingo, carrying a cargo of iron ore, is known to have been sunk by the storm off the coast of West Bengal, but liferafts have been sighted and it is believed that the crew were able to evacuate safely.

Evacuees being disembarked from a truck at a relief camp, near Berhampur in Orissa. Bikas Das/AP.

Tropical storms are caused by solar energy heating the air above the oceans, which causes the air to rise leading to an inrush of air. If this happens over a large enough area the inrushing air will start to circulate, as the rotation of the Earth causes the winds closer to the equator to move eastwards compared to those further away (the Coriolis Effect). This leads to tropical storms rotating clockwise in the southern hemisphere and anticlockwise in the northern hemisphere.These storms tend to grow in strength as they move across the ocean and lose it as they pass over land (this is not completely true: many tropical storms peter out without reaching land due to wider atmospheric patterns), since the land tends to absorb solar energy while the sea reflects it.

People beginning to clear up after Cyclone Phailin in Bhubaneswar, Orissa. PTI

The low pressure above tropical storms causes water to rise there by ~1 cm for every millibar drop in pressure, leading to a storm surge that can overwhelm low-lying coastal areas, while at the same time the heat leads to high levels of evaporation from the sea - and subsequently high levels of rainfall. This can cause additional flooding on land, as well as landslides, which are are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.

The village of Arjipalli in Orissa in the aftermath of Cyclone Phailin. AP.

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