Tuesday 15 October 2019

Typhoon Hagibis kills at least 73 people in Japan.

A total of 73 people have now been confirmed dead after Typhoon Hagibis made landfall in Japan's densely populated Kantō Region on 12 October 2019. The storm had been a Category 5 (a storm with sustained winds in excess of 254 km per hour) between 7 and 10 October, but then began to subside and was only a Category 2 storm (storm with sustained winds of between 154 and 176 km per hour) when it made landfall on the Izu Peninsula, still the most severe storm to hit the region since 1958. In addition to the known casualties at least 12 more people are missing and more than 200 injured. Low lying areas of the Kantō Region have suffered extensive flooding, more that 270 000 households have been left without power, around 110 000 without water and about 30 000 people have been unable to return to their homes due to flooding and damage.

Flooding near the Chikuma River, which burst its banks as Typhoon Hagibis battered the Kantō Region of Japan on 12 October 2019. Reuters.

Tropical storms are caused by the warming effect of the Sun over tropical seas. As the air warms it expands, causing a drop in air pressure, and rises, causing air from outside the area to rush in to replace it. If this happens over a sufficiently wide area then the inrushing winds will be affected by centrifugal forces caused by the Earth's rotation (the Coriolis effect). This means that winds will be deflected clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere, eventually creating a large, rotating Tropical Storm. They have different names in different parts of the world, with those in the northwest Pacific being referred to as typhoons.

 Flooding close to the Isuzu River in Ise, central Japan, after heavy rainfall caused by Typhoon Hagibis. Reuters/Kyodo News.

Despite the obvious danger of winds of this speed, which can physically blow people, and other large objects, away as well as damaging buildings and uprooting trees, the real danger from these storms comes from the flooding they bring. Each drop millibar drop in air-pressure leads to an approximate 1 cm rise in sea level, with big tropical storms capable of causing a storm surge of several meters. This is always accompanied by heavy rainfall, since warm air over the ocean leads to evaporation of sea water, which is then carried with the storm. These combined often lead to catastrophic flooding in areas hit by tropical storms.

 Cleanup opperations following Typhoon Hagibis in Japan. Getty Images.

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