Three people have been confirmed dead after Tropical Storm Kai-Tek swept across the Philippines on Saturday 16 December 2017. The storm made landfall on Samar Island, where 77 000 people have been evacuated from low lying areas, and seven people are known to have been injured amid widespread flooding. All three confirmed deaths occurred on the neighbouring island of Leyte, and include a woman killed by a landslide, a three-year-old boy who drowned and another person who was sucked down a manhole. Two further deaths have been reported on the islands of Biliran and Dinagat, though authorities have not yet been able to confirm these.
Flooding in Eastern Samar Province on Samar Island, the Philippines, in the wake of Tropical Storm Kai-Tek. Rhoda Baris/Rappler.
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 passage of Tropical Storm Kai-Tek till 12.00 noon GMT on Saturday 16 December 2017 (thick line) with its predicted future path (thin line, circles represent the margin of error on the predictions). Colours indicate the strength of the storm. Tropical Storm Risk.
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.
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