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| Sunday, 18 January 2004 |
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Features |  |
| News Business Features Editorial
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Swirling circles of disaster by Rehana Amidon Cyclones, typhoons, galeforce winds, floods, drought, and other natural calamities bringing death and destruction in their wake.... Sri Lanka has experienced her fair share of these calamities. But a newcomer has quite unobtrusively entered the scene and has been making quite a violent stir the past few years. Tornadoes. Nature's most violent and hazardous storms also known as 'twisters'. Common to the United States where 800 to 1200 occur every year, Canada, Southern Brazil, South Africa, Eastern and Western Australia, Bangladesh, Europe, Japan, India and New Zealand these swirling currents of destruction is not common to Sri Lanka, or so one might assume. But face the facts. A recent Department of Meteorology study reveals that there are approximately 10 to 20 tornadoes occurring in Sri Lanka every year. Though not as violent as they are often deemed to be or as devastating as those experienced in the USA, several tornadoes have been recorded in Sri Lanka over the past few years. The most devastating were: - In Kotmale on April 5, 2001 which damaged 20 houses. All the recorded incidents had taken place during the inter-monsoon seasons from March to April and October to November, where lightening activity is relatively high. Lightening is one of the most common characteristic associated with tornadoes and large thunderstorms known as supercells which cause natural disasters. A tornado is an intense rotating column of air that rises into a cloud extending from a thunderstorm to the ground. Its first step of creation starts in a thunderstorm also characterised as rising air called updraughts which supplies warm and humid air. This process of rapid development begins in a particular cloud called Cumulonimbus. At times the column of rising air becomes a vortex and is known as a funnel cloud or tornado and can create strong tornadoes with up to 300 mph wind speeds. A tornado is located on the edge of the updraught and is capable of sucking dust, debris, dirt, trees, houses, humans and even the most heaviest vehicles. This turns the funnel cloud darker. As the tornado forms, the funnel continues to grow from the cloud toward the ground. This phenomenon is also referred to as 'twister'. Tornado which form over water are called 'water spouts'. In Sri Lanka, tornadoes are considerably small in size, the average being 50 to 100 metres wide fuelled with destructive powerful winds which can exceed up to 200kmph and travel for 4 or 5 miles and lasts for about five to 10 minutes. Compared to the United States, which experiences several severe tornadoes each year, Sri Lanka produces only mild tornadoes with light or moderate damage to houses, trees and surroundings. Though it follows the same phenomena as typhoons, cyclones, and hurricanes, tornadoes differ according to the particular geographic region. According to research carried out by scientists, United States has conditions favourable for the development of tornadoes and often produce monstrous 'twisters' that last for hours and cause widespread deaths, injuries and incredible damage to properties. However large tornadoes are not always strong and can be weak at times, while tornadoes can be violent. Met Department officials point out that it is important to remember that the size of a tornado is not necessarily an indication of its intensity. Every year, the National Weather Service in USA receives about 1000 tornado touch down. Forecasters watch out for signs of any tornado ingredients forming in the sky and when there is a possibility, immediately a tornado watch (or warning) is issued. The National Weather Service in USA is equipped with the latest high-tech satellite and computer technology facilities to provide the latest information and immediately send the message automatically through electronic media. Forecasters use facilities such as a Fujita scale to rank tornadoes from 1 to 5 by damage Doppler radar systems to obtain accurate early weather warnings. Recently a group led by Huge J. Christian of the Marshall Space Flight Centre lifted a NASA detector called the Optical Transient Detector into the earth's orbit, to record the rate of lightning flashes in large storms with the hope of providing early tornado warnings. In addition, Tornado Hunters (a group of scientists and researchers) travels vast distance across the USA plains equipped with cameras and other facilities to detect tornadoes and send out warning. Unfortunately the understanding of tornadoes in Sri Lanka is very limited, and this is further hampered by the lack of weather system facilities. Meteorologists are able to forecast different cloud formations which might show signs of a possible storm threat. The Department of Meteorology has asked for a Doppler Radar, a comprehensive computer system, and high resolution satellite picture facilities from Japanese funds for expansion and improvement of weather forecasting in Sri Lanka. Guide to Tornado Safety 1. Designate an area in your home as a shelter. Disaster Supplies 1. Flashlight |
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