Nargis formed into a tropical cyclone on April 27, 2008, in the central Bay of Bengal about 360 miles off the southeast coast of India. Cyclone Nargis was, when it made landfall around the mouth of the Ayeyawaddy (Irrawaddy) river, about 220 kilometres south-west of Rangoon, a Category four storm on the Saffir-Simpson scale of hurricane strength, with sustained winds of 132 mph. Nargis is the deadliest cyclone to hit Asia since 1991, when 143,000 people perished in Bangladesh from a land-falling cyclone that year. The formation of Tropical Cyclone Nargis in the Bay of Bengal coincides with the start of cyclone season in the North Indian Ocean, which typically runs from April through December.
Burma, devastated by Nargis, is undergoing a natural and human disaster. As Tropical Cyclone Nargis swept over the Irrawaddy River Delta, pummelling the area with high winds, storm surge, and heavy rains, many tens of thousands of people have lost their lives. The Associated Press noted that a Burma state-run radio station reported on May 5, that more than 22,464 people were confirmed dead, and thousands were missing. Burma is isolated from the rest of the world at the best of times. Due to the nature of the disaster, the large area involved and the secrecy and mistrust of the Burmese government, it is impossible to get an accurate recording of the tragic human loss, but some are estimating lives lost in the hundreds of thousands, rather than the tens. This puts the Nargis disaster on a par with the 2004 boxing day tsunami which killed 300,000 people.
Tropical cyclones are amongst the most powerful and destructive meteorological systems on earth. They are a product of the interaction of between the atmosphere and the oceans. The pressures recorded at the centres of tropical cyclones are among the lowest that occur on Earth's surface at sea level.
Despite the long season, the region, which includes the Bay of Bengal and the Arabian Sea, on average has just over five named storms per year, with only two becoming full tropical cyclones. Tropical cyclones are compact, circular storms, generally some 320 km (200 miles) in diameter, whose winds swirl around a central region of low atmospheric pressure. The winds are driven by this low-pressure core and by the rotation of the Earth, which deflects the path of the wind through a phenomenon known as the Coriolis force. As a result, tropical cyclones rotate in an anti-clockwise (or cyclonic) direction in the Northern Hemisphere and in a clockwise (or anticyclonic) direction in the Southern Hemisphere.
During World War II, tropical cyclones were informally given women's names by US Army Air Corp and Navy meteorologists (after their girlfriends or wives) who were monitoring and forecasting tropical cyclones over the Pacific. From 1950 to 1952, tropical cyclones of the North Atlantic Ocean were identified by the phonetic alphabet (Able-Baker-Charlie-etc. While tropical cyclones can produce extremely powerful winds and torrential rain, they are also able to produce high waves and damaging storm surge. Although their effects on human populations can be devastating, tropical cyclones can also relieve drought conditions.
Tropical cyclones are known by various names in different parts of the world. In the North Atlantic Ocean and the eastern North Pacific they are called hurricanes, and in the western North Pacific around the Philippines, Japan, and China the storms are referred to as typhoons. In the western South Pacific and Indian Ocean they are variously referred to as severe tropical cyclones, tropical cyclones, or simply cyclones. All these different names refer to the same type of storm.
With increasing global temperatures adding energy to the earth's weather systems there is a chance that storms on the scale of Nargis may become more common place, once again hugely impacting vast populations living in vulnerable coastal and delta regions of the world.
Mark Boardman BSc dip.hyp is a leading author and expert on World Weather. For more information about Hurricanes, feel free to visit these sites.
