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Posts Tagged ‘Bhola cyclone’

Tropical Cyclones

Posted by feww on May 6, 2008

What’s a Tropical cyclone?

A tropical cyclone is a storm system characterized by a low pressure center and numerous thunderstorms that produce strong winds and flooding rain. A tropical cyclone feeds on the heat released when moist air rises and the water vapor it contains condenses.

The term “tropical” refers to both the geographic origin of these systems, which form almost exclusively in tropical regions of the globe, and their formation in Maritime Tropical air masses. The term “cyclone” refers to such storms’ cyclonic nature, with counterclockwise rotation in the Northern Hemisphere and clockwise rotation in the Southern Hemisphere. Depending on their location and strength, tropical cyclones are referred to by other names, such as hurricane, typhoon, tropical storm, cyclonic storm, tropical depression and simply cyclone.


Map of the cumulative tracks of all tropical cyclones during the 1985–2005 time period.

Tropical cyclones can produce extremely powerful winds and torrential rain, as well as high waves and devastating storm surge. They develop over large bodies of warm water, and can cause significant damage to coastal regions flooding up to 40km from the coastline. Although inland regions are relatively safe from receiving strong winds, heavy rains can produce significant flooding inland. (Source)

Cyclones can relieve drought conditions

Known for devastating human populations, tropical cyclones can also relieve drought conditions. They also carry heat and energy away from the tropics and transport it towards temperate latitudes, which makes them an important part of the global atmospheric circulation mechanism. As a result, tropical cyclones help to maintain equilibrium in the Earth’s troposphere, and to maintain a relatively stable and warm temperature worldwide. (Source)


Structure of a tropical cyclone (Source: NOAA)

Cyclone Structure

Tropical cyclones are areas of low atmospheric pressure near the Earth’s surface. The pressures recorded at the centers of tropical cyclones are very low. Tropical cyclones are driven by the release of large amounts of latent heat of condensation, which occurs when moist air is carried upwards and its water vapor condenses.

Eye and inner core

A strong tropical cyclone will harbor an area of sinking air at the center of circulation. If this area is strong enough, it can develop into an eye. Weather in the eye is normally calm and free of clouds, although the sea may be extremely violent. The eye is normally circular in shape, and may range in size from 3 km to 370km in diameter. (Source)

Brief History:

The 1970 Bhola cyclone is the deadliest tropical cyclone on record, killing more than 300,000 people and potentially as many as 1 million after striking the densely populated Ganges Delta region of Bangladesh on November 13, 1970. Its powerful storm surge was responsible for the high death toll. The North Indian cyclone basin has historically been the deadliest basin, with several cyclones since 1900 killing more than 100,000 people, all in Bangladesh. Super Typhoon Nina caused major damage and deaths in China, mainly from the collapse of the Banqiao Dam. Hundreds of thousands of people died due to the resulting floods, making it one of the deadliest tropical cyclones recorded in history. The collapse of the dam due to heavy floods also caused a string of 60 or so smaller dams to collapse. (Source)

Global Warming and Hurricanes

Source: Geophysical Fluid Dynamics Laboratory

The strongest hurricanes in the present climate may be upstaged by even more intense hurricanes over the next century as the earth’s climate is warmed by increasing levels of greenhouse gases in the atmosphere. […]
According to a new simulation study by a group of scientists at NOAA’s Geophysical Fluid Dynamics Laboratory (GFDL), a 5-12% increase in wind speeds for the strongest hurricanes (typhoons) in the northwest tropical Pacific is projected if tropical sea surfaces warm by a little over 2°C (Figure 1). Recent preliminary findings indicate that these results may apply to the other tropical cyclone basins as well. […] (Source: OAR NOAA)

Recent Cyclones and Hurricanes:

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Myanmar Cyclone Death Nearly 4,000

Posted by feww on May 5, 2008

Update #1: Deadly Nargis Cyclone

“The confirmed number is 3,934 dead, 41 injured and 2,879 missing within the Yangon and Irrawaddy divisions,” Myanmar TV reported.

“The death toll only covers two of the five disaster zones where U.N. officials said hundreds of thousands of people were without shelter and drinking water in the impoverished Southeast Asian country.” (Source)

Related Links:

For more information on tropical cyclones see: Tropical Cyclones

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