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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