Sunday 20 September 2020

Cyclone Ianos kills at least two in the Thesaly Region of Greece.

Two people are known to have died and a third is missing after Cyclone Ianos swept across the Thessaly Region of Greece on Friday 18-Saturday 19 September 2020. Winds of up to 120 km per hour have been reported, along with widespread flooding and several landslides. The dead have been described as an elderly woman who drowned in her home, and a 63-year-old shepherd who was swept away by floodwaters. Another woman is currently missing after ignoring advice by emergency services and driving into an area with high floodwaters. Around 600 people have had to be evacuated due to flooding in the areas where they lived, with about 2500 more trapped in their homes by floodwaters. Train services connecting the north and south of the country have had to be suspended, as have many flights and ferry services. A health centre in the town of Mouzaki is reported to have collapsed after a river burst its banks flooding the town, with several other buildings and bridges damaged. Emergency services are also attempting to locate a boat believed to be carrying at least 40 migrants which was last seen in the western Peloponnese.

A collapsed building in Thesaly following the passage of Cyclone Ianos. Eurokinissi/Rex/Shutterstock.

Cyclones 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.

Flood damage near the town of Karditsa in Thesaly. OTP.

The low pressure above such 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.