Thirty one people are known to have died and several dozen more are missing after Typhoon Molave made landfall near the city of Da Nang in central Vietnam on Wednesday 28 October 2020. The bodies of twelve fishermen whose boat sank off the Vietnamese coast as the storm approached were recovered on Thursday 29 October. However, the majority of the fatalities occurred in central Quang Nam Province, where three villages, were hit by a series of landslides; so far 19 bodies have been discovered here, but many more are missing and it is expected that the number of dead will rise as the debris are cleared away. The storm is also reported to have damaged around 90 000 homes and left 700 communities without electricity and clean water.
Vietnam has been hit by an unprecedented series of tropical storms this year, with seven Typhoons and several tropical storms (significant storms, but not large enough to be classified as Typhoons) having hit the country this year, In October alone the coast of Vietnam was hit by an unnamed Tropical Depression on the 7th with Tropical Storm Linfa on the 10th, Typhoon Nangka on the 14th, Tropical Storm Ofel on the 17th, and Typhoon Molave on the 28th, with Typhoon Saundel having made landfall in South China on the 24th after passing along the Vietnamese coast. This has resulted in widespread flooding in central Vietnam, and at least 36 deaths. A sharp increase in the number of tropical storms hitting Vietnam, combined with the inundation of coastal areas by rising seawaters, has been predicted as a likely outcome of rising global temperatures by the Intergovernmental Panel on Climate Change, with the country considered to be one of the most vulnerable nations to the impact of climate change.
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.
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. Landslides 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. These combined often lead to catastrophic flooding in areas hit by tropical storms.
See also...
Follow Sciency Thoughts on Facebook.
Follow Sciency Thoughts on Twitter.
