Thursday 3 October 2013

At least eight dead after Typhoon Wutip hits Vietnam.

Typhoon Wutip made landfall in central Vietnam on Monday 30 September 2013, brining with it high winds and widespread flooding. Over 300 mm of rain fell within 24 hours in parts of the country. The known death toll in the country currently stands at eight, with over 200 injured, though local authorities fear that this will rise further. Over 200 000 homes are understood to have been either destroyed by the typhoon, or submerged by flooding, and there has been extensive damage to the country's power and communication systems. Large areas of farmland are understood to have been inundated, causing extensive damage to crops and considerable loss of livestock.

Damage caused by Typhoon Wutip in central Vietnam. APP.

Chinese authorities are still searching for 58 missing fishermen from a fleet of vessels that encountered the storm near the Paracel Islands in the South China Sea on 29 September, sinking at least two vessels.  The storm has also brought widespread flooding to Laos, Cambodia and Thailand. 

A life-raft from the fishing vessel Yuetaiyu 62116 which sank in the South China Sea after encountering Typhoon Wutip on 29 September 2013. Xinhua.

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.

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.

A home destroyed by Typhoon Wutip in central Vietnam. Vietnam Investment Review.

Follow Sciency Thoughts on Facebook.