Derecho - A Killer Wind Storm from Heaven - Research Paper Example

1.0 Introduction. Derechos are windstorms with bow shaped thundershowers known to wreak extensive damage to human and natural habitat falling in their path. Derechos can have multiple or single bow echoes and are also called ‘downburst clusters.’ These downbursts 240 miles in length, having an average lifespan of 9.2 hours, are categorized as progressive, serial or hybrid depending upon their origin, shape and size. 1.1 Purpose of the Study In this paper, we have studied the typical climactic conditions that give rise to derechos, their kinds, the geographical areas visited by them, impacts on economy and ecology and what they mean to the meteorologists and the people. It was revealed during the study that though derechos are a well studied phenomenon their knowledge remains largely restricted to scientists and meteorologists. 1.2 Sources Accessed In our study, we studied different sources from research journals, news items, general awareness and meteorological reports available on the Internet. These sources helped develop a comprehensive view about derechos formation, its definition, and losses caused The sources accessed to complete the paper are: http://www.colorado.edu/hazards/awards/paper-competition/walker_grad.pdf http://www.sciencedaily.com/videos/2006/0602-derecho.htm http://vortex.weather.brockport.edu/~rochette/meso_presentations_2008/derechos_leach.ppt#1 http://www.spc.noaa.gov/misc/AbtDerechos/derechofacts.htm http://www.nationmaster.com/encyclopedia/Derechos http://www.aos.wisc.edu/uwaosjournal/Volume3/AOS453/FCS_Buerger.pdf 3.0 Discussion. 3.1 Definition. Derecho typically a Northern Hemisphere warm season phenomenon is a bow echo like storm travelling in a straight line. It has a span of a few miles. Derecho is induced by atmospheric convection. Gusts of winds travel at high speeds with a front-end of a curved bow echo like formation. Etymologically, the word derecho is derived from Spanish term ‘derecho’ meaning ‘straight forward.’ The term derecho was first used by physicist, Gustavus Hinrichs, in a paper published in American Meteorological Journal in 1888. Similarly, tornado is derived from the Spanish word ‘tornar’ meaning ‘turning around’. Minimum speed for a windstorm to be classified as a derecho is 57 mph. Severe speeds commonly associated with derechos fall in band of 90 mph to 100 mph. But they can at times exceed 100 mph and in rare cases are known to touch 155 mph. The wind speeds are not constant and vary from one point to another on the derecho path. Understandably, the high velocity of derechos winds is the main cause of the damage inflicted by this weather phenomenon. 3.2 Causes of Formation The latest studies suggest that derechos owe their origin to Mesoscale Convective Systems (MCS), a kind of thunderstorms created out of migrating low pressure systems. . The squall lines create sustained downbursts as they progress. Derechos form along stationary fronts sandwiched west- east between moist and warm air on the south and cool dry air to the north. 3.3 Types of Derechos According to their formation, derechos are classified as progressive, serial and hybrid. Progressive derechos have a short curved squall line varying from 40 to 240 miles that is perpendicular to the direction of the wind. Boundary waters-Canadian Derecho reported on July 4-5, 1999 is a kind of progressive derechos. In serial derechos squall line is parallel to wind direction with a short single bow echo. They are associated with weak low pressure systems Downburst activity is noted in the bulging part of the squall line creating an extensive sweep in serial derechos. Embedded super cells or rotating thunderstorms can also form tornadoes in serial derechos. Such serial derechos create weak tornado like events as they travel. Hybrid, as the name suggests, are derechos that display characteristics that are a combination of serial and progressive derechos. 3.4 Geography and Climatology According to climatology, derechos are a band of rapidly moving single or multiple bow shaped showers occur in the warm weather on the ‘Corn belt’ lying east of Rockies.. This region spans Ohio and Mississippi valleys and extends to southern Plains. The southern regions of Canada too are prone to derechos. North American cities Milwaukee, Rochester, Cleveland, Pittsburg, Windsor, St. Louis, and Detroit have recorded derechos events at three or more occasions in recent times. In cool weather conditions, derechos formation occurs in south-eastern states including Texas. South east and winter derechos have been observed to occur over Florida, Louisiana, the Gulf of Mexico and the Caribbean Sea. 4. 0 Atmospheric and Surface Temperature Conditions. Derechos are produced by low pressure convective systems due to relative humidity and wind speeds in the midtroposhpere. The convective instability essential for derechos formation is created by diurnal heating and low level moisture. With this derechos come to possess a quasi-stationary east-west oriented thermal boundary. 4.1 Worldwide Reach Whereas not many incidents of derechos have t been reported out of western hemisphere, a massive derechos visited Germany in 2002. In Bangladesh and adjoining parts of India, a progressive derechos called Nor’wester locally occur in springtime. Derechos do not induce major climactic change in atmospheric system of the earth. Thus their causes and effects are largely restricted to the north western hemisphere. 5.0 Economic and Ecological Impacts Derechos are known to cause large scale devastation of flora and fauna. Flora bears the maximum brunt of derechos as gusts uproot not only individual trees but also destroy forests. In 1995, winds at speeds of 77 mph destroyed one million acres of forest area in Ontario, New York , and New England besides uprooting tens of millions of stand alone trees some of them more than hundred years old. Most of the casualties and injuries, due to derechos, occur in the open due to falling trees, transmission poles, flying debris of fences and roofs. As a result areas visited by derechos bear frequent power outages causing economic and social loss. Trekkers, outdoor campers and motorists are vulnerable to derechos. Motor vehicles and mobile homes get turned upside down. Tents temporary structures erected for recreational use are torn asunder and cause injuries to the people nearby. Outhouses, barns and rickety shelters collapse in face of rampaging winds. In homes, derechos related accidents are caused by falling trees, tearing down of windows and doors resulting in injury due to flying debris, shards of panes and framework. Meteorologists suggest moving to safe places indoors away from windows, doors and attics to duck damaging derechos winds. Derechos cause rise of high waves in lakes leading to fatalities in boating. A large number of boating accidents resulting in drowning due to capsizing of boats have been reported. Such incidents have been largely reported from Great Lakes. Social losses of death and injury caused by derechos are comparable to hurricane. Little or no knowledge of disastrous effects of derechos in public practically makes it a killer on the prowl. 300 hundred deaths have been reported from 70 derechos incidents studied over past few years. Similarly other losses caused by derechos and their correlation are used to classify a windstorm as a derecho. 6.0 Summary: Derechos us a severe warm weather condition that affects North American continent. Derechos not known to affect global climatic conditions do make a severe impact on the straight paths they traverse. Derechos uproot high and weak temporary structures, uproot trees transmission and towers and turn vehicles upside down thus disturbing normal human activity. Though a phenomenon studied intensely by weathermen and scientists, the intricacies of its complicated mechanism are unknown to the public. Forecasting Derechos may not be sufficiently possible but identification and timely intervention can save a lot of damage to life and limb. Resembling bow echoes they are broad winged thundershowers that travel hundreds of travel miles at high speeds above before culminating. Public can be alerted from darkening skies with bow like formation. The casualty figure of derechos is comparable to hurricanes. This makes the meteorologists call them ‘little-known giant windstorms.’ Read More