Seventeen people are still missing after Cyclone Mekunu swept across the Yemeni Socotra Island group on Wednesday 23-Thursday 24 May 2018. Full details of the missing persons have not been released, but it is understood that four were members of the crew of one of two vessels that sank during the strom, while another three were in a car that was swept away by floodwaters. The storm is expected to make landfall on the southern part of the Arabian Peninsula this weekend, either in eastern Yemen or southern Oman.
Receding floodwaters on Socotra Island (the largest island of the Socotra group) on 24 May 2018. Abdullah Morgan/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.
The passage of Cyclone Mekunu till 12.00 GMT on Thursday 24 May 2018 (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.
See also...
Follow Sciency Thoughts on Facebook.
