Monday 13 October 2014

At keast six dead as Cyclone Huhud hits Indian east coast.

Six people are known to have died and 350 000 people have been evacuated from coastal areas after Cyclone Huhud hit the city of Visakhapatnam on the coast of Andhra Pradesh State, India, on Sunday 12 October 2014. Three deaths were recorded in Andhra Pradesh, and three in Odisha State (formerly Orissa), which is to the north, and many low lying coastal areas have been inundated by as much as 2 m of water. Sustained wind speeds as high as 205 kilometers per hour were recorded as the storm passed over Visakhapatnam (a sustained wind speed implies that this wind speed was maintianed fro over a minute), making the storm a Catagory 3 Cyclone. For many years such cyclones have been associated with very high mortality rates in India, but the practice of mass evacuations implemented in the past few years has sharply reduced the death toll.

A man rescuing a woman from a storm surge on a beach in Gopalpur, Odisha. Reuters.

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 path og Cyclone Huhud as it passed over the Indian Coast. Joint Typhoon Warning Center/National Atmospheric and Oceanic Administration.

 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...

Parts of the Indian city of Mumbai are suffering from flooding after being hit by a series of freak waves on Thursday 12 June 2014. The waves occurred around high tide, and rose over four meters above expected levels, inundating low lying coastal parts of the city and causing damage to homes and vehicles, as well as dumping considerable amounts of...

 At least thirteen people have been killed by lightning in West Bengal during the last week, and over twenty more have been injured as the annual kalboishakhi storms swept across the state. Most of those who have died were farm workers caught in the open in the Murshidabad...

 Fifteen people have been injured, two seriously, as Cyclone Bejisa moved past the island of RĂ©union (an overseas department of France in...

Follow Sciency Thoughts on Facebook.